Photo: Daniel Schwen · CC BY-SA 4.0Simpson gets more rain and snow than 83% of U.S. towns: 50 inches of precipitation a year
Sunny July days climb to about 88°. Winter and summer sit 63° apart. Its July heat outdoes that of 68% of U.S. towns. Seedlings are safe outdoors from about April 14, with the first autumn frost due around October 21.
A year in Simpson at a glance
Each month’s typical high and low, and what it brings.
What stands out about Simpson’s climate
Compared with towns across the U.S., with Simpson’s place in Illinois beside it.
What a year in Simpson feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 189 frost-free days a year
In half of years the last 32° night comes by April 14 and the first by October 21. Frost and day counts come from NOAA’s station at Dixon Springs Agric Ctr, IL, 5 miles from the town’s center, 140 ft higher.
The 2023 USDA map puts Simpson’s center in zone 7a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 2°. 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 7 inches of snow a winter
Snow, measured at Dixon Springs Agric Ctr, IL, falls mostly in February. Precipitation (rain plus melted snow) adds up to 50 inches a year; April is the wettest month and August the driest. Rain or snow falls on about 98 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Simpson
75% of the work is heating. Months averaging under 55° run from November through March.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Dixon Springs Agric Ctr, IL.
Living with Simpson’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
189 frost-free days in zone 7a. The last frost comes by Apr 14 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: April, May, September and October.
Parks & trails →Of the yearly building losses FEMA expects in Simpson from natural hazards, river flooding is the largest share (33%); heat waves, cold waves, winter storms and ice storms together are 15%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Simpson and similar climates
TownRatings has no climate map of the towns around Simpson yet.
Climates most like Simpson’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Simpson, IL | 26° | 88° | 50" | 7.2" |
| Clarksville, IN | 25° | 88° | 49" | 4.3" |
| Springdale, AR | 26° | 89° | 48" | 6.5" |
| Norristown, PA | 23° | 88° | 48" | 7.6" |
| Monett, MO | 24° | 89° | 47" | 6.7" |
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 Simpson averaged 0.9° warmer than the 1900s. The biggest change is in February (+1.9°).
A smaller shift than in 85% 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 Simpson compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Simpson’s place among Illinois’.
Simpson weather by month
Highs, lows and precipitation from NOAA’s grid at Simpson’s center; snow, wet days and snow on the ground from Dixon Springs Agric Ctr, IL. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | 30-yr range |
|---|---|---|---|---|---|---|
| January | 42° | 26° | 3.7" | 1.7" | 8 | 27° – 43° |
| February | 47° | 29° | 3.5" | 3.2" | 8 | 27° – 47° |
| March | 57° | 37° | 4.7" | 0.6" | 9 | 40° – 61° |
| April | 69° | 46° | 5.2" | 0.0" | 10 | 51° – 62° |
| May | 77° | 56° | 5.0" | 0.0" | 10 | 61° – 73° |
| June | 85° | 64° | 4.5" | 0.0" | 8 | 69° – 79° |
| July | 88° | 68° | 4.4" | 0.0" | 8 | 73° – 84° |
| August | 88° | 66° | 3.2" | 0.0" | 6 | 72° – 83° |
| September | 81° | 58° | 3.4" | 0.0" | 6 | 65° – 75° |
| October | 70° | 46° | 3.8" | 0.3" | 7 | 54° – 64° |
| November | 56° | 36° | 4.3" | 0.0" | 8 | 39° – 53° |
| December | 46° | 29° | 4.0" | 1.4" | 9 | 25° – 47° |
| Year | 67° | 47° | 49.7" | 7.2" | 98 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 25° to 47°. October is the most reliable, staying within 10°.
Where Simpson’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 Simpson’s center.
- Snow: Dixon Springs Agric Ctr, IL.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Dixon Springs Agric Ctr, IL, 5 miles from the town’s center, 140 ft higher; the nearest station that passes our checks for distance, height and agreement with the grid.
- 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 Simpson’s climate
What is the weather like in Simpson?
A typical July afternoon reaches 88°, a January night drops to 26°, and about 7 inches of snow falls in a normal winter. Milder January nights than 64% of U.S. towns; hotter July afternoons than 68% of U.S. towns.
How cold does it get in Simpson in winter?
January nights average 26°. About 80 nights a year reach 32° or below. In the coldest January of the last 30 years the month averaged 27°.
How much snow does Simpson get?
About 7.2 inches in a normal winter at Dixon Springs Agric Ctr, IL, most of it in February.
How hot does it get in Simpson?
July, with a typical high of 88° and a low of 68°. About 47 days a year reach 90° and 2 reach 100° (Dixon Springs Agric Ctr, IL).
When is the first and last frost in Simpson?
In half of years the last spring frost (32°) comes by April 14 and the first fall frost by October 21, about 189 frost-free days, at Dixon Springs Agric Ctr, IL.
What growing zone is Simpson in?
Zone 7a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 2°.
What is the best time of year to visit Simpson?
By one simple rule (highs of 62–84° and lows of 40° or more), April, May, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Simpson getting warmer?
Yes: 1991–2020 averaged 0.9° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 85% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Simpson.
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.