Climate Comfort Score
78/100
Good
NOAA 1991–2020 normals 55°F annual avg Public-domain federal data
Charleston, IL Climate
Average temperature, precipitation, and a comfort score, drawn from NOAA NCEI 1991–2020 normals →
- 55°F
- Avg annual temp
- 78/100
- Comfort score
- 43.8"
- Annual precip
- 191d
- Growing season
30-year climate normals from 1 weather station (1991-2020).
The climate verdict for Charleston
Charleston, Illinois averages 55°F a year and scores 78/100 on the comfort index - good, milder than 74% of U.S. cities.
- 55°F
- annual average temperature (NOAA normal)
- 78/100
- comfort score, milder than 74% of U.S. cities
- 43.8"
- annual precipitation · 19" snow
- 191 days
- frost-free growing season
Based on NOAA U.S. Climate Normals (1991–2020) - 30-year averages describing the typical year, not a forecast.
Avg Temperature
55°F (13°C)
Avg High
66°F
Avg Low
45°F
Annual Precip
43.8"
Annual Snow
19.0"
Comfort Score
78/100
Good
Avg Annual Temperature
55°F
30-year mean (NOAA NCEI)
Annual Precipitation
43.8"
Plus 19.0" of snow
Comfort score vs national 100-point ceiling (Charleston) 78.0%
National median (63)
PlainClimate composite, temperature mildness, humidity, precipitation, extreme-weather frequency. Good for the Charleston area.
How Charleston compares to every U.S. city
Charleston's comfort score vs. all U.S. cities
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
78 Top 26% higher than 74% of 6,915 US cities
Each bar is a band; taller bars hold more US cities. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Warming context for Charleston
MethodologySince 1900, U.S. land temperatures have tracked (and diverged from) the global mean - the chart below shows how. Charleston's current NOAA 1991-2020 normal sits within that longer spread, and the most recent decade runs warmer than the 30-year mean.
- United States land mean (NOAA NCEI) +0.11 °C/decade
- Global anomaly (NASA GISTEMP) +0.11 °C/decade
- Paris Agreement thresholds 1.5°C / 2.0°C
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Snow | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|---|
| January | 38°F (3°C) | 21°F (-6°C) | 29°F (-1°C) | 2.5" | 8.1" | 25.9 | 0.0 |
| February | 43°F (6°C) | 25°F (-4°C) | 34°F (1°C) | 2.7" | 5.5" | 21.3 | 0.0 |
| March | 54°F (12°C) | 34°F (1°C) | 44°F (7°C) | 3.1" | 1.3" | 14.9 | 0.0 |
| April | 67°F (20°C) | 44°F (7°C) | 56°F (13°C) | 5.1" | 0.3" | 4.0 | 0.0 |
| May | 77°F (25°C) | 54°F (12°C) | 66°F (19°C) | 4.5" | 0.0" | 0.2 | 1.2 |
| June | 86°F (30°C) | 63°F (17°C) | 74°F (23°C) | 4.8" | 0.0" | 0.0 | 7.5 |
| July | 88°F (31°C) | 66°F (19°C) | 77°F (25°C) | 4.4" | 0.0" | 0.0 | 11.4 |
| August | 87°F (30°C) | 64°F (18°C) | 76°F (24°C) | 2.9" | 0.0" | 0.0 | 8.8 |
| September | 81°F (27°C) | 57°F (14°C) | 69°F (21°C) | 3.1" | 0.0" | 0.0 | 4.3 |
| October | 69°F (21°C) | 46°F (8°C) | 57°F (14°C) | 3.9" | 0.0" | 2.9 | 0.3 |
| November | 54°F (12°C) | 35°F (2°C) | 45°F (7°C) | 3.7" | 0.8" | 12.7 | 0.0 |
| December | 42°F (6°C) | 26°F (-3°C) | 34°F (1°C) | 2.8" | 3.0" | 22.7 | 0.0 |
Monthly Precipitation
Average monthly rainfall and snowfall
January 2.5"
Snow: 8.1"
10.2 days with precipitation
February 2.7"
Snow: 5.5"
8.3 days with precipitation
March 3.1"
Snow: 1.3"
10.7 days with precipitation
April 5.1"
Snow: 0.3"
12.0 days with precipitation
May 4.5"
12.9 days with precipitation
June 4.8"
10.4 days with precipitation
July 4.4"
9.2 days with precipitation
August 2.9"
8.1 days with precipitation
September 3.1"
7.8 days with precipitation
October 3.9"
9.5 days with precipitation
November 3.7"
Snow: 0.8"
10.5 days with precipitation
December 2.8"
Snow: 3.0"
10.6 days with precipitation
Frost Dates & Growing Season
First Fall Freeze
October 23
50% probability date
Last Spring Freeze
April 15
50% probability date
Growing Season
191 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
4,930
Higher = more heating needed
Cooling Degree Days
1,337
Higher = more cooling needed
Warmest Month
July
Coldest Month
January
What Charleston's climate means for you
Charleston runs 55°F a year - peaking in July, coldest in January.
- Gardeners get about 191 frost-free days, with the last spring freeze near April 15 - plan the planting calendar around it, not the regional average.
- Energy bills track 4,930 heating and 1,337 cooling degree days a year, higher means the furnace or AC runs more.
- Comparing places to live? Line this city up against nearby cities and the national rankings. See rankings
These are 30-year NOAA normals (1991–2020) - the typical year, not a forecast for any specific season.
Climate Guides
Climate Insight: Charleston, IL
Charleston, Illinois runs an annual average of 55°F, ranging from a mean daily high of 66°F to a mean daily low of 45°F, per NOAA's 1991–2020 climate normals. July is typically the warmest month of the year, while January is the coldest. Drawn from station USC00111436, these thirty-year averages smooth out year-to-year swings into a baseline for what a typical month looks like here.
Anyone planning to live, garden, or travel in Charleston should weigh precipitation alongside temperature: the annual average runs 43.8 inches, with 19.0 inches typically falling as snow. The frost-free season averages 191 days, which directly shapes the planting calendar and growing potential for the area, with the last spring freeze near April 15 and the first fall freeze near October 23. And on the energy front, 4,930 heating degree days and 1,337 cooling degree days tell the story of how often furnaces and air conditioners run during a normal year.
On PlainClimate's composite comfort index, Charleston scores 78/100 (Good), a blended measure that weighs temperature mildness, precipitation moderation, and extreme-weather frequency against one another. The monthly tables above are the practical planning tool: mild highs and lows land in the shoulder seasons, July-driven heat peaks in summer, and January-driven cold sets in over deep winter. These are thirty-year averages, not a forecast - any single year can run warmer, wetter, drier, or cooler than the normal.
Frequently Asked Questions
What is the average temperature in Charleston, IL? ▼
The average annual temperature in Charleston, Illinois is 55°F. The warmest month averages 88°F (31°C) and the coldest averages 21°F (-6°C).
How much rain does Charleston get? ▼
Charleston receives 43.8 inches of precipitation annually, including 19.0 inches of snow. Based on NOAA 30-year climate normals (1991-2020).
What is the comfort score for Charleston? ▼
Charleston has a climate comfort score of 78/100 (Good), milder than 74% of U.S. cities in the PlainClimate database.
When is the growing season in Charleston? ▼
Charleston has approximately 191 frost-free days per year, with the last spring freeze around April 15 and the first fall freeze around October 23.
How much energy does heating and cooling require in Charleston? ▼
Charleston has 4,930 heating degree days and 1,337 cooling degree days annually, a heating-dominated climate. See our <a href="/guides/reading-weather-data/" class="underline hover:text-brand-600">guide to reading weather data</a> for what these figures mean.
Where does this Charleston climate data come from? ▼
NOAA U.S. Climate Normals v1.0.1 (1991-2020), from weather station USC00111436 near Charleston.
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). Station: USC00111436. For informational purposes only.
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainClimate Editorial
Every figure on PlainClimate is rendered directly from NOAA 1991-2020 U.S. Climate Normals data, no number is typed in by an editor. This page draws directly on NOAA 1991-2020 U.S. Climate Normals data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.