Irwin, SD climate
Irwin has cold, snowy winters and warm summers. A typical July afternoon reaches 88°, a January night drops to 11°, and about 45 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Irwin feels like
Winter
Spring
Summer
Fall
Irwin 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 | 30-yr range |
|---|---|---|---|---|---|---|
| January | 32° | 11° | 0.4" | 6.8" | 3 | 14° – 37° |
| February | 37° | 15° | 0.6" | 8.5" | 4 | 12° – 35° |
| March | 48° | 24° | 1.1" | 5.3" | 5 | 24° – 50° |
| April | 59° | 34° | 2.7" | 5.4" | 8 | 38° – 52° |
| May | 70° | 45° | 3.7" | 0 | 10 | 53° – 64° |
| June | 80° | 56° | 3.9" | 0 | 10 | 63° – 73° |
| July | 88° | 62° | 2.7" | 0 | 7 | 66° – 82° |
| August | 85° | 60° | 2.8" | 0 | 7 | 66° – 76° |
| September | 77° | 50° | 2.2" | 0 | 6 | 58° – 69° |
| October | 62° | 37° | 1.8" | 1.7" | 6 | 41° – 55° |
| November | 47° | 24° | 0.7" | 6.9" | 4 | 25° – 45° |
| December | 35° | 15° | 0.5" | 10.4" | 4 | 13° – 31° |
| Year | 60° | 36° | 23.2" | 45.0" | 77 |
“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 Irwin
Irwin gets 23 inches of rain and melted snow a year. June is the wettest month and January the driest. Rain or snow falls on about 77 days a year.
About 149 frost-free days a year
In half of years the last 32° night comes by May 6 and the first one by October 3. That leaves about 149 frost-free days for gardens, shorter than 82% of U.S. towns.
Heating and cooling a home in Irwin
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Irwin, 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.
Irwin and its neighbors
Irwin borders 4 towns with climate data. January nights across them vary by 0.5°. Sully has both the coldest January nights (11°) and the hottest July afternoons (88°). Irwin’s January low is 11° and its July high 88°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Irwin 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 Irwin averaged 1.3° warmer than the 1900s. The biggest change is in January (+3.6°). The shift is larger than in 53% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Irwin’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 24° to 50°. June is the most reliable, staying within 10°.
Common questions about Irwin’s climate
What is the coldest month in Irwin?
January, with a typical high of 32° and a low of 11°.
What is the hottest month in Irwin?
July, with a typical high of 88° and a low of 62°. About 29 days a year reach 90°.
How much snow does Irwin get?
About 45 inches in a normal winter, most of it in December.
When is the first frost in Irwin?
In half of years the first 32° night comes by October 3, and the last spring frost by May 6.
What is the rainiest month in Irwin?
June, with 3.9 inches of rain and melted snow. The year totals 23 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Irwin itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Gregory, SD (8 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.