lane county climate

Introduction

Lane County lies in between the Oregon Coast and the Northern Cascade Mountain Range. It is within both Climate Division 1 (Oregon Coast), Climate Diviation 2 (Willamette Valley) and Climate Division (Northern Cascade) established by the National Climatic Data Center. Below is a description of the climate of Division 1, 2 and 4 followed by specific descriptions of Lane County. Climate tables for various parameters, as observed at long-term climate stations in Lane County, are included below

Climate Division 1 — Oregon Coast

Stretching along Oregon's Pacific border, the coastal zone is characterized by wet winters, relatively dry summers, and mild temperatures throughout the year. Coastal terrain features include a coastal plain (extending from less than a mile to a few tens of miles in width), numerous coastal valleys, and the Coast Range, whose peaks range from 2,000 to 5,500 feet above sea level and extend down the full length of the state. Rivers such as the Coquille, Umpqua, and Yaquina dissect the Coast Range and drain its slopes. The area's heavy precipitation results from moist air masses moving off the Pacific Ocean onto land, especially during winter months. The abundant moisture supports lush pastures for dairy and animal production as well as valley crops of grass seed, flower bulbs, nuts, and fruit.

Along the lower elevations of the immediate coast, normal annual precipitation is between 65 to 90 inches. However, spots high on the west slopes of the range may get up to 200 inches. Several days of abundant rainfall can cause strong flood events. In some locations, flood control dams have greatly reduced the incidence of damaging floods. As is typical of western Oregon, the highest monthly precipitation values for the coast occur in the winter months of November, December, and January. Table 1 is a summary of mean monthly and annual precipitation for recording stations in the coastal zone. Figure 1 shows NOAA climate stations in Zone 1, which were in operation during the 1961-1990 period. Figure 2 shows the Lane County region from the Oregon annual precipitation map. Table 2a and 2b lists the average number of days with precipitation amounts exceeding certain thresholds.

Snowfall' in tcoastal vicinity is minimal, usually only one to three inches. Some of the higher elevations receive significant amounts of snowfall, however. For example, in January of 1982, Laurel Mountain (elevation 3,589') received 55 inches of snow. At Mary's Peak (elevation 4,097'), the highest peak in the Coast Range, snow often lasts into May. Table 4 lists average monthly and annual snowfall totals for various stations.

The months of July, August, and September tend to be the warmest, but average summer temperatures are only about 15 degrees above the coldest month, January.

Table 3 lists normal monthly temperature at stations in the area. Average heating and cooling degree days (base 65 deg F) are lower for the coastal region than any other Oregon region as a result of the mild temperatures.

Extremely high or low temperatures are rare, and the annual temperature range is lower than any other Oregon climate zone. Temperatures of 90 deg F or above occur, on the average, less than once per year, and freezing temperatures are infrequent. Newport, for example, records temperatures of 32 deg F or below an average of 30 times per year. Killing frosts are even less frequent. Most of the area averages more than 300 days between the last occurrence (in spring) and the first occurrence (in fall) of 28 deg F temperatures. Table 5 and 6 list median frost dates and mean growing seasons, respectively, for four different temperature thresholds.

Occasional strong winds strike the Oregon Coast, usually in advance of winter storms. Wind speeds can exceed hurricane force, and in rare cases have caused significant damage to structures or vegetation. Damage is most likely at exposed coastal locations, but it may extend into inland valleys as well. Such events are typically short-lived, lasting less than one day.

Skies are likely to be cloudy during winter, and only partly cloudy during summer. At Astoria, average winter cloud cover is over 80 percent, dropping only to about 65 percent in summer. Summer cloud cover is due mostly to fog and low clouds. As a result of the persistent cloudiness, total solar radiation is lower here than in any other part of the state.

Table 7 and 8 list average monthly and annual heating and growing degree days, respectively.

Climate Division 2 -- Willamette Valley

The Willamette Valley is the most diverse agricultural area in the state of Oregon, and also the home of the majority of the population. Oregon's three largest cities, Portland, Salem, and Eugene, are located in the north, central, and south portions of the Valley, respectively. The urban areas are surrounded by varied and productive ranches, orchards, and farms. Among the crops grown in significant quantities are tree fruits, nuts, berries, mint, grains, and hay. Livestock operations are also common, including the dairy and poultry industries.

The climate of the Valley is relatively mild throughout the year, characterized by cool, wet winters and warm, dry summers. The climatic conditions closely resemble the Mediterranean climates, which occur in California, although Oregon's winters are somewhat wetter and cooler. Growing seasons in the Willamette Valley are long, and moisture is abundant during most of the year (although summer irrigation is common).

Like the remainder of western Oregon, the Valley has a predominant winter rainfall climate. Typical distribution of precipitation includes about 50 percent of the annual total from December through February, lesser amounts in the spring and fall, and very little during summer. Rainfall tends to vary inversely with temperatures -- the cooler months are the wettest, the warm summer months the driest. Figure 1 shows NOAA climate stations in Zone 1, which were in operation during the 1961-1990 period. Figure 2 shows the Lane County region from the Oregon annual precipitation map.

There is considerable variation in precipitation in the Valley, ranging from annual totals below 40 inches in the Portland area to upwards of 80 inches in the Cascade and Coast Range foothills. Elevation is the single most important determinant of precipitation totals. Table 1 shows a plot of monthly & annual average precipitation versus elevation for stations in the Valley, and indicates a strong correlation between the two. Even in the lower sections of the Valley the effects of elevation are pronounced. Portland, for example, at 21 feet above sea level, receives an average of 37.4 inches (30-year normal), while Salem (196 feet) receives 40.4 inches and Eugene (359 feet) receives 46.0 inches. Thus, a change of only 338 feet of elevation produces an increase of 23 percent above Portland's total. Table 2a and 2b list the average number of days with precipitation amounts exceeding certain thresholds.

Table 3 lists normal monthly temperature at stations in the area. Extreme temperatures in the Valley are rare. Days with maximum temperature above 90 deg F occur only 5-15 times per year on average, and below zero temperatures occur only about once every 25 years. Mean high temperatures range from the low 80's in the summer to about 40 deg F in the coldest months, while average lows are generally in the low 50's in summer and low 30's in winter. The mean growing season (days between 32 deg F temperatures) is 150-180 days in the lower portions of the Valley, and 110-130 days in the foothills (above about 800 feet). Table 6 lists the mean growing season for Zone 2.

Although snow falls nearly every year, amounts are generally quite low. Valley floor locations average 5-10 inches per year, mostly during December through February, although higher totals are observed at greater elevations in the foothills. Table 4 lists average monthly and annual snowfall totals for various stations.

Table 5 lists the median frost dates for Zone 2. Severe storms are rare in the Valley. Ice storms occasionally occur in the northern portions of the Valley, resulting from cold air flowing westward through the Columbia Gorge. High winds occur several times per year in association with major weather systems.

Relative humidity is highest during early morning hours, and is generally 80-100 percent throughout the year. Humidity is generally lowest during the afternoon, ranging from 70-80 percent during January to 30-50 percent during summer. Annual pan evaporation is about 40 inches, mostly occurring during the period April - October.

Winters are likely to be cloudy. Average cloud cover during the coldest months exceeds 80 percent, with an average of about 26 cloudy days in January (in addition to 3 partly cloudy and 2 clear days). During summer, however, sunshine is much more abundant, with average cloud cover less than 40 percent; more than half of the days in July are clear.

Tables 7 and 8 list average monthly and annual heating and growing degree days, respectively.

Climate Division 4 -- Northern Cascade

The Cascade Mountains, the dominant terrain feature in Oregon, encompass the entire length of the state from the California border to Washington. With average elevations in excess of 4,000 feet, the Cascades are crowned with a number of very high peaks. Mount Hood, near the Washington border, exceeds 11,000 feet, while Mt. Jefferson and the Three Sisters exceed 10,000 feet. Mt. McLoughlin near Medford is approximately 9,500 feet. The Cascades are a higher and more imposing topographic feature in the northern part of Oregon, however. Average elevations and the number of tall peaks (over 9,000 feet) are higher north of about 43.5 deg N latitude. The region extending northward from this latitude to the Columbia River and encompassing high elevations west of the Cascade crest is the fourth of nine Oregon climatic zones.

The northern Cascades exert a profound effect on Oregon climate and weather. Mid-latitude storms approaching from the west are forced to rise as they encounter the Cascades, resulting in large amounts of orographic (terrain-induced) precipitation on the western slopes. So effective are the Cascades in removing moisture from the Pacific air masses, however, that most of Oregon east of the Cascades lies in a "rain shadow," resulting in large areas with annual precipitation less than 12 inches. Most of the northern Cascades, on the other hand, receive an excess of 80 inches per year; the highest peaks collect more than 150 inches per year, most of it in the form of snow. As in the case of rest of western Oregon, most of the precipitation in the Northern Cascades falls during the winter months with November through March period accounting for more than 75 percent of the total annual precipitation. Spring and fall rain and snow and summer thunderstorms contribute to the annual precipitation total, but they are dwarfed by the winter precipitation totals. Table 1 lists monthly and annual normal precipitation at Zone 4 sites.

Tables 2a and 2b list the average number of days with precipitation amounts exceeding certain thresholds.

Table 4 lists average monthly and annual snowfall totals for various stations. Monthly mean snowfall totals vary significantly according to elevation. Since precipitation tends to increase with increasing elevation, more potential moisture for snowfall is available at higher elevations. Since temperatures generally decrease with increasing elevation, those high precipitation amounts are more likely to be in the form of snow. As an example, McKenzie Bridge (elevation 1400 feet) receives an average of about 42 inches snow per year, while Marion Forks (2,500 feet) receives about 150 inches and Government Camp (3,980 feet) about 300 inches per year. Figure 1 shows NOAA climate stations in Zone 4, which were in operation during the 1961-1990 period. Figure 2 shows the Lane County region from the Oregon annual precipitation map.

Table 3 lists normal monthly temperature at stations in the area. The correlation of temperature with elevation is quite strong, with the highest station (Government Camp) having consistently lower temperatures than the other sites. McKenzie Bridge has by far the highest annual mean maximum temperatures, but its annual average temperature is only slightly higher than Detroit Dam due to lower minimum temperatures at McKenzie.

Table 5 and 6 list median frost dates and mean growing seasons, respectively, for four different temperature thresholds. Detroit Dam, at an elevation of 1,220 feet, has an exceptionally long growing season. This is probably due to the fact that its location above the valley floor prevents significant accumulation of cold air on clear nights, and the presence of nearby Detroit Lake serves to moderate any low temperatures. The growing season at higher elevation sites such as McKenzie Bridge, Marion Forks, and Belknap Springs is only about 50 percent as long as at Detroit: for example, Marion Forks at 2,480 feet has an average of only 116 days between occurrences of 32deg F temperatures compared with 244 days at Detroit Dam.

Tables 7 and 8 list average monthly and annual heating and growing degree days, respectively.

County Description

Established: Jan. 28, 1851
Population: 325,900
Area: 4,620 sq. mi.
Economy: Agriculture, higher education, high technology, forest products, recreation, RV manufacturing and tourism.
County Seat: Eugene

Lane County was named for Gen. Joseph Lane, a rugged frontier hero who was Oregon's first territorial governor. Pioneers traveling the Oregon Trail in the late 1840s came to Lane County mainly to farm. The county's first district court met under a large oak tree until a clerk's office could be built in 1852. A few years later, the first courthouse opened in what is now downtown Eugene. With the building of the railroads, the market for timber opened in the 1880s. Today, wood products are still an important part of the economy in addition to high-tech manufacturing and tourism. Lane County government operates under a home rule charter approved by voters in 1962. Although 90 percent of Lane County is forestland, Eugene and Springfield comprise the second largest urban area in Oregon.

(County information obtained from Oregon Blue Book)

Climate Tables (Lane County, Oregon)


Table 1. Precipitation, Monthly and Annual Averages (1971-2000) (back to top)
Name
Number
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
Cottage Grove 1 S
1897
6.51
5.40
5.20
4.00
2.81
1.53
0.60
0.92
1.48
3.22
7.27
6.96
45.9
Cottage Grove Dam
1902
6.89
5.84
5.48
4.32
3.15
1.67
0.68
0.97
1.68
3.66
7.77
7.46
49.57
Dorena Dam
2374
6.21
5.41
5.29
4.34
3.25
1.81
0.75
1.03
1.80
3.39
7.42
6.73
47.43
Eugene WSO Airport
2709
7.65
6.35
5.80
3.66
2.66
1.53
0.64
0.99
1.54
3.35
8.44
8.29
50.9
Fern Ridge Dam
2867
6.42
5.49
4.72
3.10
2.17
1.39
0.53
0.70
1.33
2.81
7.18
7.64
43.48
Honeyman State Park
3995
10.83
9.34
8.96
5.24
3.80
2.47
0.92
1.14
2.27
5.34
10.76
11.96
73.03
Leaburg 1 SW
4811
8.87
7.78
7.31
5.88
4.25
2.68
0.86
1.14
2.48
4.95
10.57
9.91
66.68
Lookout Point Dam
5050
6.03
5.21
5.05
4.23
3.47
2.12
0.79
1.10
1.76
3.28
7.11
6.57
46.72
Mc Kenzie Bridge
5221
10.54
8.90
7.32
5.37
3.98
2.67
1.11
1.08
2.27
4.91
11.21
11.54
70.9
Mc Kenzie Bridge R S
5362
9.24
7.99
7.11
5.75
4.13
2.85
1.00
1.42
2.71
4.97
10.89
10.68
68.74
Oakridge Fish Hatchery
6213
6.31
5.05
4.82
4.08
3.01
1.78
0.66
1.04
1.64
3.29
7.17
6.88
45.73

Table 2a. Average number of Days with Selected Precipitation Amounts, Eugene WSO Airport, 1971-2000 (back to top)
Threshold
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
.01"or more
17.1
15.9
17.3
14.2
10.8
7.4
3.2
4.1
5.9
10.9
17.7
17.3
141.8
.10"or more
11.9
11.3
12.0
8.9
7.1
4.1
1.5
2.1
3.7
7.0
13.2
12.6
95.3
.50"or more
5.3
4.3
4.1
2.1
1.4
0.8
0.3
0.6
1.0
2.0
6.2
5.7
33.8
1.00"or more
2.1
1.4
1.2
0.6
0.3
0.2
0
0.2
0.2
0.6
2.5
2.3
11.5
Table 2b. Average number of Days with Selected Precipitation Amounts, Honeyman State Park, 1971-2000 (back to top)
Threshold
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
.01"or more
18.2
17.9
18.2
16.6
12.4
8.6
4.7
5.3
6.8
11.4
19.4
19.8
165.5
.10"or more
14.8
14.5
14.9
11.7
8.1
5.3
2.3
2.7
4.3
8.6
16
15.8
121.9
.50"or more
7.4
6.8
6.6
3.9
2.7
1.4
0.6
0.6
1.4
4.0
8.2
8.2
52.1
1.00"or more
3.2
2.6
2.3
0.9
0.6
0.5
0.1
0.2
0.4
1.4
3.2
3.6
18.4

Table 3. Monthly and Annual Average Temperatures (deg F), Eugene WSO Airport (1862), 1971-2000 (back to top)
Parameter
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
Mean max
46.5
50.7
55.9
60.6
66.8
73.3
81.5
81.9
76.6
64.6
52.1
45.7
63.0
Mean min
33.0
34.9
36.7
38.9
42.7
47.0
50.8
50.8
46.7
40.5
37.2
33.3
41.0
Mean temp
39.8
42.8
46.3
49.8
54.8
60.2
66.2
66.4
61.7
52.6
44.7
39.5
52.1
Extreme max
67
72
77
81
93
102
105
108
103
94
76
68
108
Extreme min
7
4
21
27
29
32
39
39
31
19
12
-12
-12
Mean number of days
Max 90 or more
0
0
0
0
0.2
1.0
5.9
5.7
2.5
0.1
0
0
15.4
Min 32 or less
13.7
9.2
5.9
2.5
0.5
0
0
0
0.2
2.3
7.4
12.5
54.2
Max 32 or less
1.3
0.3
0
0
0
0
0
0
0
0
0.2
1.4
3.2
Min 0 or less
0
0
0
0
0
0
0
0
0
0
0
0.2
0.2

Table 4. Snowfall, Monthly and Annual Averages (1971-2000) (back to top)
Name
Number
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
Cottage Grove 1 S
1897
1.0
1.5
0.2
0
0
0
0
0
0
0
0.2
0.9
3.5
Cottage Grove Dam
1902
1.0
2.1
0.2
0
0
0
0
0
0
0
0.1
0.3
3.9
Dorena Dam
2374
1.0
2.0
0.3
0.1
0
0
0
0
0
0
0.1
0.7
4.4
Eugene WSO Airport
2709
1.5
1.6
0.1
0
0
0
0
0
0
0
0.2
1.4
4.7
Fern Ridge Dam
2867
0.1
0.5
0
0
0
0
0
0
0
0
0.1
1
1.8
Honeyman State Park
3995
0.1
0.5
0
0
0
0
0
0
0
0
0
0.3
1.0
Leaburg 1 SW
4811
1.4
1.8
0.2
0
0
0
0
0
0
0
0.3
1.1
4.6
Lookout Point Dam
5050
0.6
0.6
0
0
0
0
0
0
0
0
0
0.7
1.8
Mc Kenzie Bridge
5221
19.9
19.2
13.7
6.3
0.5
0
0
0
0
0.4
9.6
18.4
91.1
Mc Kenzie Bridge R S
5362
6.8
6.8
2.4
0.1
0
0
0
0
0
0.1
1.8
4.7
29.9
Oakridge Fish Hatchery
6213
1.6
1.8
0.5
0.1
0
0
0
0
0
0
0.6
1.5
7.2

Table 5. Median Spring and Fall Frost Dates, Eugene WSO Airport, 1971-2000 (back to top)
Percentile
Last Date in Spring of Low Temperatures (deg F)
First Date in Fall of Low Temperatures (deg F)
24
28
32
36
24
28
32
36
10
19-Jan
8-Feb
24-Mar
30-Apr
8-Nov
21-Oct
29-Sep
22-Sep
20
30-Jan
22-Feb
5-Apr
9-May
13-Nov
29-Oct
7-Oct
25-Sep
50
8-Feb
9-Mar
24-Apr
22-May
10-Dec
26-Nov
18-Oct
4-Oct
80
1-Jan
30-Mar
9-May
2-Jun
31-Dec
18-Dec
29-Oct
14-Oct
90
1-Jan
6-Apr
17-May
10-Jun
31-Dec
20-Dec
8-Nov
18-Oct

Table 6. Average Growing Season, Eugene WSO Airport, 1971-2000 (back to top)
Percentile
Length of Time (Days) Between Occurrence of Temperatures ( deg F)
24
28
32
36
10
-37
207
149
116
20
-7
221
159
123
50
301
259
179
139
80
693
288
200
151
90
711
299
210
159

Table 7. Monthly and Annual Average Heating Degree Days (base 65°F), 1971-2000 (back to top)
Name
Number
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
Cottage Grove 1 S
1897
753
599
571
452
317
166
63
60
148
368
585
757
4858
Cottage Grove Dam
1902
793
635
608
483
343
184
71
58
144
379
622
799
5123
Dorena Dam
2374
793
635
608
483
343
184
71
58
144
379
622
799
5123
Eugene WSO Airport
2709
769
615
566
442
308
151
40
32
115
370
598
779
4786
Fern Ridge Dam
2867
795
624
571
459
320
143
51
35
119
341
603
776
4895
Honeyman State Park
3995
646
527
533
449
350
242
165
145
175
330
514
657
4792
Leaburg 1 SW
4811
757
609
569
441
304
156
54
45
125
347
590
771
4769
Lookout Point Dam
5050
741
589
549
432
302
153
49
38
107
315
555
737
4565
Mc Kenzie Bridge
5221
1002
828
789
625
453
247
112
118
265
529
809
1004
6786
Mc Kenzie Bridge R S
5362
932
721
659
473
292
125
37
39
147
439
744
890
5696
Oakridge Fish Hatchery
6213
833
660
617
472
324
162
58
55
147
386
665
845
5227

Table 8. Monthly and Annual Average Growing Degree Days (base 50°F), 1971-2000 (back to top)
Name
Number
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Annual
Cottage Grove 1 S
1897
6
13
23
65
168
300
462
466
321
125
25
7
1981
Cottage Grove Dam
1902
3
7
19
55
152
283
461
476
331
123
17
4
1931
Dorena Dam
2374
4
8
20
65
162
292
467
474
325
123
19
5
1964
Eugene WSO Airport
2709
7
10
22
65
173
320
518
526
367
127
24
6
2165
Fern Ridge Dam
2867
3
5
22
62
168
337
506
524
364
149
18
4
2162
Honeyman State Park
3995
9
19
24
50
123
209
302
322
282
147
32
9
1528
Leaburg 1 SW
4811
2
9
26
77
184
322
498
507
356
145
19
2
2147
Lookout Point Dam
5050
4
12
33
80
187
323
513
523
383
170
30
7
2265
Mc Kenzie Bridge
5221
0
0
2
25
104
235
408
395
212
52
0
0
1433
Mc Kenzie Bridge R S
5362
0
1
7
70
207
364
545
532
333
84
3
0
2146
Oakridge Fish Hatchery
6213
0
3
17
68
174
314
484
488
332
121
7
1
2009