Photo: Steven Pavlov · CC BY-SA 4.0Few U.S. towns get less rain and snow than Coulee Dam: 11 inches a year
Peak summer warmth arrives in July, with afternoons near 88°. The seasons are far apart: from a winter night to a summer afternoon the average spans 67°. By July afternoons alone, it runs hotter than 69% of U.S. towns. Garden planting can start around April 22; autumn frost returns near October 21.
A year in Coulee Dam at a glance
Each month’s typical high and low, and what it brings.
What stands out about Coulee Dam’s climate
Compared with towns across the U.S., with Coulee Dam’s place in Washington beside it.
What a year in Coulee Dam feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 180 frost-free days a year
In half of years the last 32° night comes by April 22 and the first by October 21. Frost and day counts come from Coulee Dam 1 Sw, WA, 1.4 miles away.
The 2023 USDA map puts Coulee Dam’s center in zone 7b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 6°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 11 inches of rain a year
December is the wettest month and August the driest.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Coulee Dam
90% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Coulee Dam 1 Sw, WA.
Living with Coulee Dam’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
180 frost-free days in zone 7b. The last frost comes by Apr 22 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 21.
Months with highs of 62–84° and lows of 40° or more: May, June and September. 1.0 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Coulee Dam from natural hazards, river flooding is the largest share (40%); heat waves, cold waves, winter storms and ice storms together are 7%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Coulee Dam and similar climates
TownRatings has no climate map of the towns around Coulee Dam yet.
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Coulee Dam averaged 0.7° warmer than the 1900s. The biggest change is in January (+3.1°).
A smaller shift than in 92% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Coulee Dam compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Coulee Dam’s place among Washington’s.
Coulee Dam weather by month
Highs, lows and precipitation from NOAA’s grid at Coulee Dam’s center. 1991–2020 normals.
| Month | High | Low | Rain + melt | 30-yr range |
|---|---|---|---|---|
| January | 33° | 22° | 1.1" | 19° – 34° |
| February | 40° | 24° | 0.8" | 21° – 40° |
| March | 52° | 30° | 1.0" | 34° – 47° |
| April | 62° | 35° | 0.9" | 44° – 56° |
| May | 72° | 43° | 1.1" | 52° – 63° |
| June | 79° | 49° | 1.0" | 60° – 72° |
| July | 88° | 55° | 0.5" | 63° – 76° |
| August | 88° | 55° | 0.3" | 66° – 74° |
| September | 78° | 47° | 0.4" | 58° – 67° |
| October | 61° | 36° | 0.8" | 43° – 54° |
| November | 44° | 28° | 1.1" | 30° – 44° |
| December | 34° | 22° | 1.4" | 21° – 33° |
| Year | 61° | 37° | 10.5" |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 21° to 40°. August is the most reliable, staying within 9°.
Where Coulee Dam’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Coulee Dam’s center.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Coulee Dam 1 Sw, WA, 1.4 miles from the town’s center, 560 ft higher; no station nearby passes every check; this is the nearest one in the same valley, flagged above.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Coulee Dam’s climate
What is the weather like in Coulee Dam?
A typical July afternoon reaches 88°, a January night drops to 22°. Colder January nights than 52% of U.S. towns; hotter July afternoons than 69% of U.S. towns.
How cold does it get in Coulee Dam in winter?
January nights average 22°. About 120 nights a year reach 32° or below and 1 reach 0° or below. In the coldest January of the last 30 years the month averaged 19°.
How hot does it get in Coulee Dam?
July, with a typical high of 88° and a low of 55°. About 33 days a year reach 90° and 3 reach 100° (Coulee Dam 1 Sw, WA).
When is the first and last frost in Coulee Dam?
In half of years the last spring frost (32°) comes by April 22 and the first fall frost by October 21, about 180 frost-free days, at Coulee Dam 1 Sw, WA.
What growing zone is Coulee Dam in?
Zone 7b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 6°.
What is the best time of year to visit Coulee Dam?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Coulee Dam getting warmer?
Yes: 1991–2020 averaged 0.7° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 92% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Coulee Dam.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.