River Sioux, IA climate
River Sioux has cold, snowy winters and warm summers. A typical July afternoon reaches 86°, a January night drops to 12°, and about 46 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in River Sioux feels like
Winter
Spring
Summer
Fall
River Sioux 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 | 31° | 12° | 0.7" | 10.0" | 8 | 19 | 13° – 35° |
| February | 36° | 17° | 0.8" | 13.4" | 8 | 19 | 15° – 36° |
| March | 49° | 28° | 1.7" | 6.9" | 9 | 6 | 31° – 54° |
| April | 62° | 38° | 3.2" | 1.9" | 10 | 1 | 42° – 56° |
| May | 73° | 50° | 4.6" | 0.3" | 14 | 0 | 56° – 67° |
| June | 83° | 61° | 4.5" | 0 | 13 | 0 | 68° – 76° |
| July | 86° | 64° | 3.3" | 0 | 10 | 0 | 70° – 82° |
| August | 84° | 62° | 3.7" | 0 | 10 | 0 | 67° – 77° |
| September | 78° | 53° | 3.3" | 0 | 10 | 0 | 59° – 71° |
| October | 64° | 40° | 2.3" | 1.0" | 9 | 1 | 45° – 57° |
| November | 48° | 27° | 1.3" | 2.3" | 6 | 2 | 28° – 49° |
| December | 35° | 17° | 1.2" | 9.8" | 7 | 13 | 13° – 32° |
| Year | 61° | 39° | 30.7" | 45.6" | 114 | 61 |
“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 River Sioux
River Sioux gets 31 inches of rain and melted snow a year. May is the wettest month and January the driest. Rain or snow falls on about 114 days a year. Snow covers the ground about 61 days of the year.
About 155 frost-free days a year
In half of years the last 32° night comes by May 1 and the first one by October 3. That leaves about 155 frost-free days for gardens, shorter than 76% of U.S. towns.
Heating and cooling a home in River Sioux
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In River Sioux, 89% of that work is heating and 11% 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 River Sioux 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 River Sioux averaged 1.1° warmer than the 1900s. The biggest change is in January (+2.4°). The shift is smaller than in 60% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at River Sioux’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. March swings the most: between 1991 and 2020 its average temperature ranged from 31° to 54°. June is the most reliable, staying within 9°.
Common questions about River Sioux’s climate
What is the coldest month in River Sioux?
January, with a typical high of 31° and a low of 12°.
What is the hottest month in River Sioux?
July, with a typical high of 86° and a low of 64°. About 26 days a year reach 90°.
How much snow does River Sioux get?
About 46 inches in a normal winter, most of it in February.
When is the first frost in River Sioux?
In half of years the first 32° night comes by October 3, and the last spring frost by May 1.
What is the rainiest month in River Sioux?
May, with 4.6 inches of rain and melted snow. The year totals 31 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for River Sioux itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Little Sioux 2 Nw, IA (2 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.