coos county climate
Introduction

Coos County lies along the southern part of the Oregon Coast. It is wholly within Climate Division 1 (Oregon Coast) established by the National Climatic Data Center. Below is a description of the climate of Division 1 followed by specific descriptions of Coos County. Climate tables for various parameters, as observed at long-term climate stations in Coos 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 Coos County region from the Oregon annual precipitation map. Table 2 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.

County Description

Established: Dec. 22, 1853
Population: 62,950
Area: 1,629 sq. mi.
Economy: Forest products, fishing, agriculture, shipping, recreation and tourism.
County Seat: Coquille

Coos County was created by the Territorial Legislature from parts of Umpqua and Jackson Counties in 1853 and included Curry County until 1855. The county seat was Empire City until 1896, when it was moved to Coquille. Although trappers had been in the area a quarter-century earlier, the first permanent settlement in present Coos County was at Empire City, now part of Coos Bay, by members of the Coos Bay Company in 1853. The name "Coos" derives from a native Coos Bay Indian tribe and translates to "lake" or "place of pines." Forest products, tourism, fishing and agriculture dominate the Coos County economy. Boating, dairy farming, myrtlewood manufacturing, shipbuilding and repair and agriculture specialty products including cranberries, also play an important role. The International Port of Coos Bay, considered the best natural harbor between Puget Sound and San Francisco, is the world's largest forest products shipping port.

(County information obtained from Oregon Blue Book)
 

Climate Tables (Coos 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
Bandon 2 NNE
471 9.22 7.76 7.39 4.61 3.16 1.63 0.43 0.90 1.63 3.88 9.13 9.71 59.45
Coquille Kwro
1836 8.70 7.29 6.92 4.47 2.94 1.38 0.41 0.69 1.49 3.50 8.87 8.93 55.59
N. Bend FAA Airport
6073 9.54 8.12 7.94 5.19 3.40 1.72 0.51 0.88 1.73 4.62 10.36 10.42 64.43
Powers
6820 9.45 8.26 7.43 5.14 2.96 1.14 0.32 0.69 1.62 3.53 8.98 9.87 59.39

Table 2. Average number of Days with Selected Precipitation Amounts, North Bend FAA Airport, 1971-2000 (back to top)
Threshold
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
.01"or more
19.0 18.1 19.7 16.6 13.0 9.6 4.7 5.4 6.6 12.1 19.9 19.3 163.5
.10"or more
15.3 14.0 14.5 11.8 7.8 4.5 1.7 2.2 3.9 8.0 15.9 15.5 114.9
.50"or more
6.7 5.6 5.8 3.0 2.3 0.8 0.1 0.5 1.1 3.2 7.4 7.3 43.7
1.00"or more
2.7 2.2 1.9 0.8 0.4 0.3 0.1 0.1 0.2 1.2 2.9 3.1 15.8

Table 3. Monthly and Annual Average Temperatures (deg F), North Bend (1862), 1971-2000 (back to top)
Parameter
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Mean max
52.7 54.6 55.5 57.4 60.9 63.8 66.6 67.6 67.2 63.0 56.7 52.8 59.9
Mean min
39.4 40.8 41.4 43.0 46.9 50.3 52.6 52.9 50.2 45.9 42.6 39.4 45.5
Mean temp
46.1 47.7 48.5 50.2 53.9 57.1 59.6 60.3 58.7 54.5 49.7 46.1 52.7
Extreme max
69 82 78 87 83 92 88 84 95 95 73 70 95
Extreme min
19 14 27 30 35 39 43 44 36 28 22 15 14
Mean number of days
Max 90 or more
0 0 0 0 0 0 0 0 0.1 0 0 0 0.1
Min 32 or less
4.7 2.7 1 0.2 0 0 0 0 0 0.2 1.7 3.6 14.2
Max 32 or less
0 0 0 0 0 0 0 0 0 0 0 0.2 0.2
Min 0 or less
0 0 0 0 0 0 0 0 0 0 0 0 0

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
Bandon 2 NNE
471 0.2 0.2 0 0 0 0 0 0 0 0 0 0.1 0.6
Coquille Kwro
1836 0.2 0 0 0 0 0 0 0 0 0 0.1 0.2 0.5
N. Bend FAA Airport
6073 0.6 0.2 0 0 0 0 0 0 0 0 0.1 0.3 1.2
Powers
6820 0.8 0.6 0.1 0 0 0 0 0 0 0 0 0.5 2.2

Table 5. Median Spring and Fall Frost Dates, North Bend, 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
1-Jan 1-Jan 16-Jan 12-Mar 19-Dec 11-Nov 2-Nov 7-Oct
20
1-Jan 1-Jan 29-Jan 25-Mar 31-Dec 11-Dec 9-Nov 16-Oct
50
1-Jan 21-Jan 26-Feb 7-Apr 31-Dec 31-Dec 29-Nov 5-Nov
80
1-Jan 8-Feb 26-Mar 26-Apr 31-Dec 31-Dec 21-Dec 26-Nov
90
29-Jan 21-Feb 5-Apr 29-Apr 31-Dec 31-Dec 28-Dec 4-Dec

Table 6. Average Growing Season, North Bend, 1971-2000 (back to top)
Percentile
Length of Time (Days) Between Occurrence of Temperatures ( deg F)
24 28 32 36
10
336 294 234 191
20
350 309 247 198
50
365 337 269 209
80
365 365 311 228
90
365 365 338 251

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
Bandon 2 NNE
471 576 489 522 458 376 260 186 176 214 344 466 580 4642
Coquille Kwro
1836 619 507 518 444 347 222 128 106 156 308 486 628 4468
N. Bend FAA Airport
6073 584 487 510 442 341 235 163 145 187 324 456 574 4454
Powers
6820 647 524 517 410 290 154 53 49 109 286 503 657 4237

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
Bandon 2 NNE
471 21 31 30 41 101 191 280 290 234 134 51 24 1431
Coquille Kwro
1836 15 28 38 59 134 231 342 365 300 167 49 16 1744
N. Bend FAA Airport
6073 20 31 34 49 129 216 302 321 266 151 54 23 1596
Powers
6820 13 26 43 89 190 311 460 467 367 196 44 12 2218