tillamook county climate

Introduction

Tillamook County lies along the northern 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 Tillamook County. Climate tables for various parameters, as observed at long-term climate stations in Tillamook 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 Tillamook 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. 15, 1853
Population: 24,600
Area: 1,125 sq. mi.
Economy: Agriculture, forest products, fishing and recreation.
County Seat: Tillamook

Tillamook County was formed in 1853 from Yamhill and Clatsop counties. The name Tillamook comes from the Tillamook (or Killamook) Indians. Dairy farms dominate the county's fertile valley. It is the home of the world-famous Tillamook Cheese Factory. The reforested, 355,000 acre "Tillamook Burn" is rapidly maturing. Commercial thinning will become increasingly evident. With 75 miles of scenic coastline, four bays and nine rivers, Tillamook County offers the finest deep-sea and stream fishing, charter and dory boats, clamming, crabbing, beachcombing and hiking. Its forests also furnish excellent hunting.

(County information obtained from Oregon Blue Book)

Climate Tables (Tillamook 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
Cloverdale
1682 11.85 9.65 9.16 6.04 4.66 3.16 1.44 1.45 3.58 6.16 12.57 12.81 82.53
Tillamook 1 W
8494 13.09 10.79 9.90 6.81 4.84 3.41 1.64 1.42 3.68 7.16 13.72 13.94 90.4

Table 2. Average number of Days with Selected Precipitation Amounts, Tillamook 1 W, 1971-2000 (back to top)
Threshold
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
.01"or more
21.7 19.5 21.5 18.4 15.8 11.4 7.8 6.8 10.7 15.1 22.3 22.3 193.2
.10"or more
17.5 16.0 17.0 13.2 11.0 7.8 3.8 3.7 6.7 10.7 18.0 18.0 143.4
.50"or more
9.2 8.0 8.0 4.6 3.2 2.1 0.9 0.8 2.7 5.2 10.3 9.6 64.6
1.00"or more
4.2 3.1 2.3 1.4 0.7 0.5 0.3 0.1 1.0 2.2 4.1 4.3 24.2

Table 3. Monthly and Annual Average Temperatures (deg F), Tillamook 1 W (1862), 1971-2000 (back to top)
Parameter
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Mean max
49.9 52.5 54.2 56.8 60.4 63.7 66.7 68.1 68.6 62.5 54.4 49.9 59.0
Mean min
36.3 37.2 37.5 39.3 43.3 47.0 49.9 49.8 46.6 41.9 39.2 36.4 42.0
Mean temp
43.1 44.9 45.9 48.1 51.9 55.4 58.3 59.0 57.6 52.2 46.8 43.2 50.5
Extreme max
69 73 73 84 86 92 93 102 97 92 73 66 102
Extreme min
11 8 21 23 25 31 36 35 27 22 14 4 4
Mean number of days
Max 90 or more
0 0 0 0 0 0.1 0.1 0.3 0.4 0 0 0 0.8
Min 32 or less
9.8 7.7 7.8 4.3 0.8 0 0 0 0.5 3.2 6.5 9.1 49.6
Max 32 or less
0.1 0.1 0 0 0 0 0 0 0 0 0 0.7 0.9
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
Cloverdale
1682 0.4 0 0.2 0.1 0 0 0 0 0 0 0.1 0.3 1.2
Tillamook 1 W
8494 0.6 0.3 0.1 0 0 0 0 0 0 0 0.2 0.2 1.4

Table 5. Median Spring and Fall Frost Dates, Tillamook 1 W, 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
29-Jan 27-Feb 10-Apr 6-May 10-Nov 8-Oct 23-Sep 6-Sep
20
2-Feb 6-Mar 15-Apr 11-May 17-Nov 20-Oct 29-Sep 8-Sep
50
14-Feb 2-Apr 1-May 3-Jun 10-Dec 8-Nov 8-Oct 18-Sep
80
5-Jun 15-Apr 13-May 18-Jun 31-Dec 26-Nov 20-Oct 4-Oct
90
1-Jan 25-Apr 25-May 29-Jun 31-Dec 29-Nov 31-Oct 12-Oct

Table 6. Average Growing Season, Tillamook 1 W, 1971-2000 (back to top)
Percentile
Length of Time (Days) Between Occurrence of Temperatures ( deg F)
24 28 32 36
10
204 194 137 73
20
247 198 146 87
50
293 217 165 104
80
365 255 172 138
90
696 266 191 152

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
Cloverdale
1682 644 538 558 472 368 252 161 139 181 344 512 648 4854
Tillamook 1 W
8494 672 563 584 498 396 279 197 179 221 396 543 673 5200

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
Cloverdale
1682 11 20 22 43 113 202 307 331 278 139 35 10 1511
Tillamook 1 W
8494 9 14 17 33 93 175 270 290 236 103 30 9 1279