Climate averages 1991–2020
Decatur weather
in July.
A hot, wet month: the warmest and the 9th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
July is a hot month in Decatur: daytime highs average 28.8°C and nights cool to about 19.9°C. By daytime temperature it is the warmest month of the year.
Expect about 91 mm of rain on roughly 10 days, which makes July a wet month (the 9th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 14 h 42 min on an average July day.
The nearest other city in this atlas is Springfield (Illinois), United States (59 km away). In July its highs average 29.1°C, about as warm as Decatur, with 91 mm of rain.
Among the 498 cities listed in the United States, Decatur ranks joint 317th of 498 for the warmest July highs and joint 318th of 498 for the driest July (rainfall, lowest first). The mean July high of those 498 cities is 30.3°C; Decatur is 1.5°C cooler than that mean.
From July to August, average highs fall by 0.5°C to 28.3°C, and monthly rainfall falls from 91 mm to 77 mm.
The annual picture
July in context
Monthly precipitation
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Decatur climate table
| Month | Average highHigh / low | Average low | Precipitation mm/month | Wet days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 1.8°C-6.3°C | -6.3°C | 69 | 8.5 | 9.710 h |
| February | 4.6°C-4.7°C | -4.7°C | 59 | 7.6 | 10.711 h |
| March | 10.7°C0.7°C | 0.7°C | 83 | 9.7 | 11.912 h |
| April | 17.2°C6.7°C | 6.7°C | 118 | 11.7 | 13.213 h |
| May | 22.5°C12.8°C | 12.8°C | 122 | 13.2 | 14.414 h |
| June | 27.1°C17.9°C | 17.9°C | 110 | 10.9 | 14.915 h |
| July, selected | 28.8°C19.9°C | 19.9°C | 91 | 10.3 | 14.715 h |
| August | 28.3°C19.3°C | 19.3°C | 77 | 8.4 | 13.714 h |
| September | 25.0°C15.4°C | 15.4°C | 82 | 7.3 | 12.512 h |
| October | 18.2°C9.1°C | 9.1°C | 88 | 8.6 | 11.211 h |
| November | 10.5°C2.3°C | 2.3°C | 88 | 8.7 | 10.010 h |
| December | 4.3°C-3.1°C | -3.1°C | 63 | 8.7 | 9.49 h |
Precipitation (rain or snow, as water) is the average of the 30 separate monthly totals. A wet day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
July in nearby cities
- Springfield (Illinois), United States in JulyUnited States · 59 kmHigh 29.1°C · Low 20.2°C · 91 mm rain
- Champaign in JulyUnited States · 68 kmHigh 28.3°C · Low 19.3°C · 92 mm rain
- Bloomington (Illinois), United States in JulyUnited States · 72 kmHigh 28.2°C · Low 19.3°C · 98 mm rain
- Peoria (Illinois), United States in JulyUnited States · 109 kmHigh 28.8°C · Low 20.1°C · 96 mm rain
- St. Louis in JulyUnited States · 172 kmHigh 31.0°C · Low 21.6°C · 86 mm rain
- Lafayette (Indiana), United States in JulyUnited States · 188 kmHigh 28.1°C · Low 19.0°C · 92 mm rain
- O'Fallon in JulyUnited States · 189 kmHigh 30.8°C · Low 21.6°C · 82 mm rain
- Joliet in JulyUnited States · 201 kmHigh 28.2°C · Low 19.1°C · 95 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Decatur) is explained once on the Decatur year overview and on the Sources, method and limits page.