Rock Island, WA climate
Rock Island has chilly winters and warm summers, with very little rain. A typical July afternoon reaches 88°, a January night drops to 24°, and about 17 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decade4° warmer than normal today. The forecast high is 74°, and a typical Oct 1 in Rock Island peaks around 70°.Live forecast: National Weather Service · Normal: NOAA 1991–2020
What a year in Rock Island feels like
Winter
Spring
Summer
Fall
Rock Island weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 36° | 24° | 1.2" | 5.6" | 10 | 13 | 22° – 35° |
| February | 43° | 27° | 0.9" | 3.0" | 7 | 5 | 25° – 42° |
| March | 54° | 32° | 0.8" | 0.4" | 6 | 1 | 39° – 50° |
| April | 63° | 38° | 0.6" | 0 | 5 | 0 | 45° – 58° |
| May | 73° | 47° | 0.7" | 0 | 6 | 0 | 54° – 66° |
| June | 79° | 53° | 0.6" | 0 | 4 | 0 | 62° – 75° |
| July | 88° | 59° | 0.3" | 0 | 2 | 0 | 66° – 78° |
| August | 87° | 58° | 0.2" | 0 | 2 | 0 | 67° – 76° |
| September | 78° | 49° | 0.3" | 0 | 2 | 0 | 60° – 69° |
| October | 63° | 38° | 0.7" | 0 | 6 | 0 | 45° – 57° |
| November | 46° | 30° | 1.0" | 1.5" | 9 | 1 | 32° – 45° |
| December | 35° | 24° | 1.5" | 6.0" | 10 | 10 | 24° – 34° |
| Year | 62° | 40° | 8.8" | 16.5" | 67 | 30 |
“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 Rock Island
Rock Island gets 9 inches of rain and melted snow a year. December is the wettest month and August the driest. Rain or snow falls on about 67 days a year. Snow covers the ground about 30 days of the year.
About 200 frost-free days a year
In half of years the last 32° night comes by April 8 and the first one by October 24. That leaves about 200 frost-free days for gardens, longer than 72% of U.S. towns.
Heating and cooling a home in Rock Island
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Rock Island, 88% of that work is heating and 12% 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 Rock Island 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 Rock Island averaged 1.3° warmer than the 1900s. The biggest change is in January (+4.1°). The shift is larger than in 59% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Rock Island’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 25° to 42°. September is the most reliable, staying within 8°.
Common questions about Rock Island’s climate
What is the coldest month in Rock Island?
December, with a typical high of 35° and a low of 24°.
What is the hottest month in Rock Island?
July, with a typical high of 88° and a low of 59°. About 35 days a year reach 90°.
How much snow does Rock Island get?
About 17 inches in a normal winter, most of it in December.
When is the first frost in Rock Island?
In half of years the first 32° night comes by October 24, and the last spring frost by April 8.
What is the rainiest month in Rock Island?
December, with 1.5 inches of rain and melted snow. The year totals 9 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Rock Island itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Wenatchee, WA (9 mi, snow) and Wenatchee Pangborn Airport, WA (3 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.