Charleston, Illinois climate: Normal weather by month, frost dates and records
Charleston's normal year runs from 21°F January nights to 88°F July afternoons, with 43.8 inches of precipitation and 19 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 12.8°C, January lows of −6°C, July highs of 31°C, 1,111 mm of precipitation a year.
- NOAA stationCharleston
- Station IDUSC00111436
- Location39.48°N 88.17°W
- Elevation700 ft (213 m)
- Population17,361
On October 23, the normal high in Charleston is 66°F and the normal low 43°F, and the chance of measurable rain or snow is 32%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Charleston.
- Jan 38° 21°
- Feb 43° 25°
- Mar 54° 34°
- Apr 67° 44°
- May 77° 54°
- Jun 86° 63°
- Jul 88° 66°
- Aug 87° 64°
- Sep 81° 57°
- Oct 69° 46°
- Nov 54° 35°
- Dec 42° 26°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Charleston each month?
July is the warmest month, with normal highs of 88°F; January the coldest, with normal lows of 21°F. The most precipitation falls in April (5.09 in), the least in January (2.54 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 38°F | 21°F | 29.3°F | 2.54 | 8.1 | 10 | <1 | 26 | 9 h 40 min |
| February | 43°F | 25°F | 33.9°F | 2.69 | 5.5 | 8 | <1 | 21 | 10 h 40 min |
| March | 54°F | 34°F | 44.0°F | 3.11 | 1.3 | 11 | <1 | 15 | 11 h 50 min |
| April | 67°F | 44°F | 55.7°F | 5.09 | 0.3 | 12 | <1 | 4 | 13 h 10 min |
| May | 77°F | 54°F | 65.6°F | 4.52 | 0.0 | 13 | 1 | <1 | 14 h 20 min |
| June | 86°F | 63°F | 74.2°F | 4.84 | 0.0 | 10 | 8 | <1 | 15 h |
| July | 88°F | 66°F | 77.2°F | 4.40 | 0.0 | 9 | 11 | <1 | 14 h 40 min |
| August | 87°F | 64°F | 75.5°F | 2.94 | 0.0 | 8 | 9 | <1 | 13 h 50 min |
| September | 81°F | 57°F | 69.0°F | 3.15 | 0.0 | 8 | 4 | <1 | 12 h 30 min |
| October | 69°F | 46°F | 57.3°F | 3.94 | 0.0 | 10 | <1 | 3 | 11 h 10 min |
| November | 54°F | 35°F | 44.6°F | 3.74 | 0.8 | 11 | <1 | 13 | 10 h |
| December | 42°F | 26°F | 34.3°F | 2.79 | 3.0 | 11 | <1 | 23 | 9 h 20 min |
| Year (annual) | 66°F | 45°F | 55.0°F | 43.75 | 19.0 | 120 | 34 | 105 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 3°C | −6°C | −1.5°C | 65 mm | 21 cm |
| February | 6°C | −4°C | 1.1°C | 68 mm | 14 cm |
| March | 12°C | 1°C | 6.7°C | 79 mm | 3 cm |
| April | 20°C | 7°C | 13.2°C | 129 mm | 1 cm |
| May | 25°C | 12°C | 18.7°C | 115 mm | 0 cm |
| June | 30°C | 17°C | 23.4°C | 123 mm | 0 cm |
| July | 31°C | 19°C | 25.1°C | 112 mm | 0 cm |
| August | 30°C | 18°C | 24.2°C | 75 mm | 0 cm |
| September | 27°C | 14°C | 20.6°C | 80 mm | 0 cm |
| October | 21°C | 8°C | 14.1°C | 100 mm | 0 cm |
| November | 12°C | 2°C | 7.0°C | 95 mm | 2 cm |
| December | 6°C | −3°C | 1.3°C | 71 mm | 8 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00111436; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Charleston?
Normal highs sit between 65°F and 85°F in April, May, September and October. Of those, September has the fewest days with rain (8).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00111436.
When is the last frost in Charleston?
In Charleston, the last spring frost (32°F) comes after April 15 in half of years and after May 3 in one year in ten; the first autumn frost comes before October 23 in half of years and before October 9 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 151 year in 10 after May 3; 9 in 10 after April 1
- First autumn frost, half of years before
- October 231 year in 10 before October 9; 9 in 10 before November 4
NOAA puts the median frost-free season at 187 days, and the season without a hard freeze (28°F) at 213 days.
A hard freeze (28°F) comes after April 3 in half of springs and before November 2 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Charleston in zone 6a in ZIP code 61920, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Charleston's NOAA station is in zone 6a: the coldest night of a typical year reaches −6°F (26 complete years).
Frost dates for every NOAA station in Illinois · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00111436; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Charleston?
In a normal year in Charleston, 34 days a year reach 90°F (1 of them 100°F or more), 105 nights fall to 32°F or colder and 120 days bring measurable precipitation.
- Days at 90°F or more
- 34a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 105a normal year
- Days that stay below freezing
- 24high of 32°F or less
- Days with 0.01 inch of precipitation
- 120a normal year
- Days with 1 inch of snow or more
- 8a normal year
The highest temperature in this station's record (since 1896) is 110°F, on July 15, 1936; the lowest is −27°F, on January 19, 1994.
The wettest calendar year on that record is 1957, with 52.83 in; the snowiest season is 1995–96, with 45.1 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00111436; records: ACIS (NOAA Regional Climate Centers), station USC00111436. Records use complete months only; a month missing more than three days is left out.
How sunny is Charleston?
Over a year 74% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Charleston, 4.1 kWh per square metre a day. July is the sunniest month (83%) and December the cloudiest (61%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 62% | 1.9 |
| February | 65% | 2.7 |
| March | 67% | 3.7 |
| April | 72% | 4.9 |
| May | 73% | 5.5 |
| June | 81% | 6.4 |
| July | 83% | 6.3 |
| August | 82% | 5.6 |
| September | 81% | 4.7 |
| October | 74% | 3.3 |
| November | 70% | 2.3 |
| December | 61% | 1.6 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Charleston need?
A normal year in Charleston brings 4,930 heating degree days, 8% fewer than the median U.S. place (5,373), and 1,337 cooling degree days, 47% more than the median (908). Six months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 4,056 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,106 | 0 |
| February | 869 | 0 |
| March | 657 | 5 |
| April | 303 | 23 |
| May | 97 | 116 |
| June | 9 | 286 |
| July | 0 | 377 |
| August | 2 | 327 |
| September | 47 | 167 |
| October | 274 | 34 |
| November | 612 | 2 |
| December | 953 | 0 |
| Year (annual) | 4,930 | 1,337 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00111436. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Charleston been warmer than normal lately?
2025 averaged 56.2°F, 1.2°F above the 1991-2020 normal of 55.0°F. 2 of the 2 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 56.1°F | +1.1°F | 48.72 | 18.1 |
| 2025 | 56.2°F | +1.2°F | 33.82 | 30.8 |
Over 89 complete years from 1897 to 2025, the station's annual mean temperature rose at a fitted 1.9°F per century (+0.11°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00111436; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Charleston's climate compare?
Charleston is warmer than 119 of the other 143 places with their own NOAA record in Illinois, and wetter than 113. Across the 7,247 U.S. stations with normals, its annual mean of 55.0°F is warmer than 60%.
In the Köppen classification computed from these normals, Charleston is Dfa: continental, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Charleston share this climate record?
4 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Oakland, IL720 people · 15 mi NE
- Kansas, IL649 people · 13 mi NE
- Ashmore, IL627 people · 9 mi NE
- Westfield, IL520 people · 9 mi E
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Charleston's climate
What is the coldest month in Charleston?
January, with a normal high of 38°F and a normal low of 21°F. The warmest is July (88°F by day, 66°F at night).
Does it snow in Charleston?
Yes: 19 inches in a normal year, falling on 12 days with 0.1 inch or more, the most in January (8.1 inches).
What is the rainiest month in Charleston?
April, with 5.09 in of precipitation in a normal year; the driest is January with 2.54 in.
What plant hardiness zone is Charleston in?
The USDA's 2023 map puts Charleston in zone 6a in ZIP code 61920, the nearest ZIP area. By the same method at Charleston's NOAA station, the coldest night of a typical year reaches −6°F (26 years, 1991-2020): zone 6a.
How late can frost come in Charleston?
In half of years the last 32°F night comes after April 15; in one year in ten it comes after May 3. Waiting until May 3 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Illinois climateThe statewide normals and every place in the state
- Mattoon, IL6 miles from this station, 53.4°F a year
- Casey, IL16 miles from this station, 54.1°F a year
- Neoga, IL20 miles from this station, 53.6°F a year
- Tuscola, IL23 miles from this station, 52.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made