Climate Comfort Score
68/100
Good
NOAA 1991–2020 normals 53°F annual avg Public-domain federal data
Decatur, IL Climate
Annual temperature, rainfall, and a comfort score, sourced from NOAA NCEI's 1991–2020 normals →
- 53°F
- Avg annual temp
- 68/100
- Comfort score
- 36.4"
- Annual precip
- 189d
- Growing season
30-year climate normals from 1 weather station (1991-2020).
The climate verdict for Decatur
Decatur, Illinois averages 53°F a year and scores 68/100 on the comfort index - good, milder than 58% of U.S. cities.
- 53°F
- average temperature, NOAA 1991-2020 normal
- 68/100
- comfort score, milder than 58% of U.S. cities
- 36.4"
- precipitation, annual total
- 189 days
- frost-free days per growing season
Based on NOAA U.S. Climate Normals (1991–2020) - 30-year averages describing the typical year, not a forecast.
Avg Temperature
53°F (12°C)
Avg High
63°F
Avg Low
43°F
Annual Precip
36.4"
Comfort Score
68/100
Good
Avg Annual Temperature
53°F
30-year mean (NOAA NCEI)
Annual Precipitation
36.4"
Liquid-equivalent total
Comfort score vs national 100-point ceiling (Decatur) 68.0%
National median (63)
PlainClimate composite, temperature mildness, humidity, precipitation, extreme-weather frequency. Good for the Decatur area.
How Decatur compares to every U.S. city
Decatur's comfort score vs. all U.S. cities
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
68 Top 42% higher than 58% 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 Decatur
MethodologyDecatur's NOAA 1991-2020 normal sits inside a longer story: U.S. land temperatures have been tracking (and drifting from) the global mean since 1900, and the chart below shows that spread, with the most recent decade running 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 | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|
| January | 35°F (2°C) | 20°F (-7°C) | 27°F (-3°C) | 2.0" | 26.5 | 0.0 |
| February | 40°F (4°C) | 23°F (-5°C) | 32°F (0°C) | 1.8" | 23.9 | 0.0 |
| March | 52°F (11°C) | 32°F (0°C) | 42°F (6°C) | 2.5" | 17.0 | 0.0 |
| April | 64°F (18°C) | 42°F (6°C) | 53°F (12°C) | 3.7" | 4.6 | 0.0 |
| May | 74°F (24°C) | 53°F (12°C) | 64°F (18°C) | 4.4" | 0.2 | 0.8 |
| June | 83°F (28°C) | 62°F (17°C) | 73°F (23°C) | 4.4" | 0.0 | 6.3 |
| July | 86°F (30°C) | 66°F (19°C) | 76°F (24°C) | 3.3" | 0.0 | 9.0 |
| August | 84°F (29°C) | 63°F (17°C) | 74°F (23°C) | 3.0" | 0.0 | 6.6 |
| September | 79°F (26°C) | 55°F (13°C) | 67°F (19°C) | 3.0" | 0.0 | 3.9 |
| October | 66°F (19°C) | 44°F (7°C) | 55°F (13°C) | 3.2" | 3.0 | 0.4 |
| November | 51°F (11°C) | 34°F (1°C) | 43°F (6°C) | 3.0" | 13.9 | 0.0 |
| December | 40°F (4°C) | 25°F (-4°C) | 32°F (0°C) | 2.1" | 23.6 | 0.0 |
Monthly Precipitation
Average monthly rainfall
January 2.0"
7.7 days with precipitation
February 1.8"
7.4 days with precipitation
March 2.5"
10.5 days with precipitation
April 3.7"
11.3 days with precipitation
May 4.4"
13.2 days with precipitation
June 4.4"
11.1 days with precipitation
July 3.3"
10.0 days with precipitation
August 3.0"
9.2 days with precipitation
September 3.0"
8.9 days with precipitation
October 3.2"
10.2 days with precipitation
November 3.0"
9.3 days with precipitation
December 2.1"
8.9 days with precipitation
Frost Dates & Growing Season
First Fall Freeze
October 22
50% probability date
Last Spring Freeze
April 16
50% probability date
Growing Season
189 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
5,393
Higher = more heating needed
Cooling Degree Days
1,105
Higher = more cooling needed
Warmest Month
July
Coldest Month
January
Humidity & Wind
Monthly averages from hourly observations
| Month | Humidity | Wind (mph) | Clear Sky % | Overcast % |
|---|---|---|---|---|
| January | 76% | 11.2 | 43% | 37% |
| February | 72% | 11.7 | 40% | 39% |
| March | 67% | 11.8 | 45% | 30% |
| April | 67% | 11.0 | 45% | 27% |
| May | 68% | 9.2 | 48% | 21% |
| June | 71% | 7.7 | 54% | 11% |
| July | 73% | 6.5 | 56% | 9% |
| August | 73% | 6.9 | 59% | 12% |
| September | 68% | 8.3 | 62% | 15% |
| October | 70% | 10.4 | 49% | 31% |
| November | 75% | 10.9 | 45% | 38% |
| December | 78% | 11.1 | 42% | 43% |
What Decatur's climate means for you
Decatur runs 53°F a year - peaking in July, coldest in January.
- Gardeners get about 189 frost-free days, with the last spring freeze near April 16 - plan the planting calendar around it, not the regional average.
- Energy bills track 5,393 heating and 1,105 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: Decatur, IL
Based on station USW00003887 feeding NOAA's 1991–2020 climate normals, Decatur, Illinois averages 53°F a year, ranging from a mean daily high of 63°F to a mean daily low of 43°F. July is typically the warmest month of the year, while January is the coldest. Because these figures are thirty-year averages rather than any single year's readings, they describe the typical month, not a forecast for it.
Anyone planning to live, garden, or travel in Decatur should weigh precipitation alongside temperature: the annual average runs 36.4 inches, predominantly as rainfall. The frost-free season averages 189 days, which directly shapes the planting calendar and growing potential for the area, with the last spring freeze near April 16 and the first fall freeze near October 22. And on the energy front, 5,393 heating degree days and 1,105 cooling degree days tell the story of how often furnaces and air conditioners run during a normal year.
On PlainClimate's composite comfort index, Decatur scores 68/100 (Good), a blended measure that weighs temperature mildness, precipitation moderation, and extreme-weather frequency against one another. The monthly tables above turn that into a planning tool: expect the mildest highs and lows in the shoulder seasons, July-driven heat at the peak of summer, and January-driven cold at the depth of winter. Every number here is a thirty-year average, not a forecast, so any given year can and does run warmer, cooler, wetter, or drier than the normal.
Frequently Asked Questions
What is the average temperature in Decatur, IL? ▼
The average annual temperature in Decatur, Illinois is 53°F. The warmest month averages 86°F (30°C) and the coldest averages 20°F (-7°C).
How much rain does Decatur get? ▼
Decatur receives 36.4 inches of precipitation annually. Based on NOAA 30-year climate normals (1991-2020).
What is the comfort score for Decatur? ▼
Decatur has a climate comfort score of 68/100 (Good), milder than 58% of U.S. cities in the PlainClimate database.
When is the growing season in Decatur? ▼
Decatur has approximately 189 frost-free days per year, with the last spring freeze around April 16 and the first fall freeze around October 22.
How much energy does heating and cooling require in Decatur? ▼
Decatur has 5,393 heating degree days and 1,105 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 Decatur climate data come from? ▼
NOAA U.S. Climate Normals v1.0.1 (1991-2020), from weather station USW00003887 near Decatur.
Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). Station: USW00003887. 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.