Grand Coulee, WA climate
Grand Coulee has chilly winters and warm summers, with very little rain. A typical July afternoon reaches 88°, a January night drops to 21°.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Grand Coulee feels like
Winter
Spring
Summer
Fall
Grand Coulee weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | 30-yr range |
|---|---|---|---|---|
| January | 33° | 21° | 1.2" | 19° – 33° |
| February | 40° | 24° | 0.9" | 21° – 39° |
| March | 51° | 30° | 1.1" | 33° – 47° |
| April | 61° | 35° | 0.9" | 43° – 55° |
| May | 71° | 43° | 1.1" | 52° – 63° |
| June | 78° | 49° | 1.0" | 60° – 71° |
| July | 88° | 55° | 0.5" | 63° – 76° |
| August | 87° | 55° | 0.3" | 65° – 74° |
| September | 77° | 47° | 0.4" | 58° – 67° |
| October | 61° | 36° | 0.9" | 43° – 54° |
| November | 44° | 28° | 1.2" | 30° – 43° |
| December | 33° | 22° | 1.6" | 21° – 33° |
| Year | 60° | 37° | 11.1" |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Grand Coulee
Grand Coulee gets 11 inches of rain and melted snow a year. December is the wettest month and August the driest.
About 180 frost-free days a year
In half of years the last 32° night comes by April 22 and the first one by October 21. That leaves about 180 frost-free days for gardens, longer than 53% of U.S. towns.
Heating and cooling a home in Grand Coulee
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Grand Coulee, 90% of that work is heating and 10% is cooling, so the furnace matters far more than the air conditioner.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
How Grand Coulee compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Grand Coulee averaged 0.7° warmer than the 1900s. The biggest change is in January (+3.1°). The shift is smaller than in 89% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Grand Coulee’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. February swings the most: between 1991 and 2020 its average temperature ranged from 21° to 39°. August is the most reliable, staying within 8°.
Common questions about Grand Coulee’s climate
What is the coldest month in Grand Coulee?
January, with a typical high of 33° and a low of 21°.
What is the hottest month in Grand Coulee?
July, with a typical high of 88° and a low of 55°. About 33 days a year reach 90°.
When is the first frost in Grand Coulee?
In half of years the first 32° night comes by October 21, and the last spring frost by April 22.
What is the rainiest month in Grand Coulee?
December, with 1.6 inches of rain and melted snow. The year totals 11 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Grand Coulee itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Coulee Dam 1 Sw, WA (1 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.