Photo: Illinois2011 · CC BY 3.0Alton’s winters are milder and less snowy than most of the U.S.
A typical July afternoon reaches 88°, a January night drops to 23°, and about 11 inches of snow falls in a normal winter.
A year in Alton at a glance
Each month’s typical high and low, and what it brings.
What stands out about Alton’s climate
Compared with towns across the U.S., with Alton’s place in Illinois beside it.
What a year in Alton feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 214 frost-free days a year
In half of years the last 32° night comes by April 4 and the first by November 5. Frost and day counts come from NOAA’s station at Alton - Melvin Price L&d, IL, 2.5 miles from the town’s center, at about the same height.
The 2023 USDA map puts Alton’s center in zone 7a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 0°. 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 11 inches of snow a winter
Snow, measured at Edwardsville 2 W, IL, falls mostly in January. Precipitation (rain plus melted snow) adds up to 42 inches a year; May is the wettest month and February the driest. Rain or snow falls on about 112 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Alton
77% 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 Alton - Melvin Price L&d, IL.
Living with Alton’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
214 frost-free days in zone 7a. The last frost comes by Apr 4 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Nov 5.
Months with highs of 62–84° and lows of 40° or more: April, May, September and October. 8.1 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Alton from natural hazards, river flooding is the largest share (38%); heat waves, cold waves, winter storms and ice storms together are 22%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Alton and its neighbors
Every town next door is within a degree of Alton in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Alton’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 |
|---|---|---|---|---|
| Alton, IL | 23° | 88° | 42" | 11" |
| Sedalia, MO | 21° | 88° | 41" | 13" |
| Louisburg, KS | 21° | 88° | 41" | 14" |
| Lake of the Woods, VA | 25° | 88° | 44" | 11" |
| Hamilton, OH | 22° | 87° | 43" | 9.7" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Alton averaged 0.8° warmer than the 1900s. The biggest change is in December (+2.1°).
A smaller shift than in 88% 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 Alton compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Alton’s place among Illinois’.
Alton weather by month
Highs, lows and precipitation from NOAA’s grid at Alton’s center; snow, wet days and snow on the ground from Edwardsville 2 W, IL. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 39° | 23° | 2.4" | 3.7" | 8 | 6 | 25° – 42° |
| February | 44° | 26° | 2.2" | 2.5" | 8 | 3 | 25° – 45° |
| March | 55° | 35° | 3.3" | 1.0" | 11 | 1 | 38° – 59° |
| April | 67° | 45° | 4.6" | 0.1" | 11 | 0 | 48° – 62° |
| May | 76° | 56° | 5.0" | 0.0" | 13 | 0 | 61° – 73° |
| June | 85° | 65° | 4.3" | 0.0" | 10 | 0 | 70° – 79° |
| July | 88° | 69° | 4.1" | 0.0" | 8 | 0 | 73° – 85° |
| August | 87° | 66° | 3.4" | 0.0" | 9 | 0 | 71° – 82° |
| September | 80° | 58° | 3.3" | 0.0" | 8 | 0 | 65° – 75° |
| October | 68° | 47° | 3.2" | 0.0" | 9 | 0 | 52° – 64° |
| November | 54° | 36° | 3.4" | 0.2" | 9 | 0 | 38° – 52° |
| December | 43° | 28° | 2.6" | 3.3" | 8 | 4 | 22° – 44° |
| Year | 66° | 46° | 41.7" | 10.8" | 112 | 15 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 22° to 44°. June is the most reliable, staying within 9°.
Where Alton’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 Alton’s center.
- Snow: Edwardsville 2 W, IL.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Alton - Melvin Price L&d, IL, 2.5 miles from the town’s center, at about the same height; 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 Alton’s climate
What is the weather like in Alton?
A typical July afternoon reaches 88°, a January night drops to 23°, and about 11 inches of snow falls in a normal winter. Milder January nights than 54% of U.S. towns; hotter July afternoons than 67% of U.S. towns.
How cold does it get in Alton in winter?
January nights average 23°. About 85 nights a year reach 32° or below and 1 reach 0° or below. In the coldest January of the last 30 years the month averaged 25°.
How much snow does Alton get?
About 11 inches in a normal winter at Edwardsville 2 W, IL, most of it in January, with snow on the ground about 15 days a year.
How hot does it get in Alton?
July, with a typical high of 88° and a low of 69°. About 29 days a year reach 90° (Alton - Melvin Price L&d, IL).
When is the first and last frost in Alton?
In half of years the last spring frost (32°) comes by April 4 and the first fall frost by November 5, about 214 frost-free days, at Alton - Melvin Price L&d, IL.
What growing zone is Alton in?
Zone 7a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 0°.
What is the best time of year to visit Alton?
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 Alton getting warmer?
Yes: 1991–2020 averaged 0.8° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 88% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Alton.
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.