Decatur weather in July: Decatur, Illinois: normal highs, lows, rain and records for July
Decatur in July has a normal high of 86°F and a normal low of 66°F, a daily mean of 76°F, holding near 86°F all month. Measurable precipitation falls on 10 days in a normal July, 3.32 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 30°C and low of 19°C, 84 mm of precipitation in July.
- NOAA stationDecatur Airport
- Station IDUSW00003887
- Location39.83°N 88.87°W
- Elevation675 ft (206 m)
- From the center4 miles
- Population68,763
- Jan 35° 20°
- Feb 40° 23°
- Mar 52° 32°
- Apr 64° 42°
- May 74° 53°
- Jun 83° 62°
- Jul 86° 66°
- Aug 84° 63°
- Sep 79° 55°
- Oct 66° 44°
- Nov 51° 34°
- Dec 40° 25°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Decatur in July?
The normal high is 86°F and the normal low 66°F, for a daily mean of 75.7°F. July is 3.0°F warmer than June and 2.0°F warmer than August. July is the warmest month of the year in Decatur and the 4th wettest. Across the month the normal high falls 1°F, from 86°F on July 1 to 85°F on July 31. From one year to the next July's mean temperature typically moves about 2.6°F either way (NOAA's standard deviation), so roughly two Julys in three average between 73°F and 78°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 35%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| July 1 | 86°F | 65°F | 35% | 20% |
| July 8 | 86°F | 66°F | 34% | 19% |
| July 15 | 86°F | 66°F | 32% | 18% |
| July 22 | 86°F | 66°F | 30% | 17% |
| July 31 | 85°F | 65°F | 29% | 16% |
Every day of July: normal high, low and chance of precipitation (warmest afternoon July 8, coldest night July 31)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| July 1 | 86°F | 65°F | 35% | 20% | 15 h |
| July 2 | 86°F | 65°F | 35% | 20% | 15 h |
| July 3 | 86°F | 66°F | 35% | 20% | 15 h |
| July 4 | 86°F | 66°F | 35% | 20% | 15 h |
| July 5 | 86°F | 66°F | 34% | 20% | 14 h 50 min |
| July 6 | 86°F | 66°F | 34% | 19% | 14 h 50 min |
| July 7 | 86°F | 66°F | 34% | 19% | 14 h 50 min |
| July 8 | 86°F | 66°F | 34% | 19% | 14 h 50 min |
| July 9 | 86°F | 66°F | 33% | 19% | 14 h 50 min |
| July 10 | 86°F | 66°F | 33% | 19% | 14 h 50 min |
| July 11 | 86°F | 66°F | 33% | 18% | 14 h 50 min |
| July 12 | 86°F | 66°F | 33% | 18% | 14 h 50 min |
| July 13 | 86°F | 66°F | 32% | 18% | 14 h 50 min |
| July 14 | 86°F | 66°F | 32% | 18% | 14 h 50 min |
| July 15 | 86°F | 66°F | 32% | 18% | 14 h 40 min |
| July 16 | 86°F | 66°F | 31% | 17% | 14 h 40 min |
| July 17 | 86°F | 66°F | 31% | 17% | 14 h 40 min |
| July 18 | 86°F | 66°F | 31% | 17% | 14 h 40 min |
| July 19 | 86°F | 66°F | 31% | 17% | 14 h 40 min |
| July 20 | 86°F | 66°F | 30% | 17% | 14 h 40 min |
| July 21 | 86°F | 66°F | 30% | 17% | 14 h 40 min |
| July 22 | 86°F | 66°F | 30% | 17% | 14 h 30 min |
| July 23 | 86°F | 66°F | 30% | 17% | 14 h 30 min |
| July 24 | 86°F | 66°F | 30% | 16% | 14 h 30 min |
| July 25 | 86°F | 66°F | 30% | 16% | 14 h 30 min |
| July 26 | 86°F | 65°F | 30% | 16% | 14 h 30 min |
| July 27 | 86°F | 65°F | 30% | 16% | 14 h 30 min |
| July 28 | 86°F | 65°F | 30% | 16% | 14 h 20 min |
| July 29 | 86°F | 65°F | 29% | 16% | 14 h 20 min |
| July 30 | 85°F | 65°F | 29% | 16% | 14 h 20 min |
| July 31 | 85°F | 65°F | 29% | 16% | 14 h 20 min |
- Normal high
- 86°FJuly average
- Normal low
- 66°FJuly average
- Precipitation
- 3.32 inmonth total
- Days with precipitation
- 100.01 inch or more
- Days at 90°F or more
- 9
- Daylight
- 15 h to 14 h 20 minJuly 1 to July 31
- Days at 70°F or more
- 31
- Days at 80°F or more
- 27
- Sunshine
- 83%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00003887; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Decatur in July?
On a given July day the chance of 0.01 inch or more is 32% on average, highest around July 1 (35%). In all, 3.32 in falls on 10 days of a normal July, 1 of them with an inch or more.
In a normal July in Decatur, 9 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00003887.
How humid and windy is Decatur in July?
At 3 p.m. the normal temperature is 84°F with 55% relative humidity and a dew point of 66°F; at 6 a.m. it is 68°F with 88% humidity. The wind averages 6.5 mph, most often from the west-southwest in the afternoon. A dew point of 65°F or more feels muggy to most people.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 68°F | 64°F | 88% | 4.7 mph | 73% |
| 9 a.m. | 78°F | 66°F | 68% | 7.7 mph | 73% |
| noon | 82°F | 66°F | 58% | 8.6 mph | 59% |
| 3 p.m. | 84°F | 66°F | 55% | 9.0 mph | 61% |
| 6 p.m. | 81°F | 66°F | 62% | 7.4 mph | 73% |
| 9 p.m. | 73°F | 66°F | 81% | 5.0 mph | 80% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00003887. Hourly normals exist only for NOAA's first-order stations; a dash where NOAA publishes no value for that hour (the sky at some hours).
What are the records for July in Decatur?
The warmest July temperature on this station's record (since 2000) is 104°F, on July 25, 2012; the coldest is 46°F, on July 2, 2001. The wettest July brought 9.16 in (2008).
The July mean against the 1991-2020 normal of 75.7°F: 2021 74.6°F (−1.1), 2022 76.5°F (+0.8), 2023 76.2°F (+0.5), 2024 75.3°F (−0.4), 2025 80.2°F (+4.5), 2026 75.8°F (+0.1). 4 of 6 ran warmer than normal.
| July | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 74.6°F | −1.1°F | 4.23 in |
| 2022 | 76.5°F | +0.8°F | 3.61 in |
| 2023 | 76.2°F | +0.5°F | 3.61 in |
| 2024 | 75.3°F | −0.4°F | 8.35 in |
| 2025 | 80.2°F | +4.5°F | 7.80 in |
| 2026 | 75.8°F | +0.1°F | 2.70 in |
Source: records: ACIS, station USW00003887; recent months: ACIS, station USW00003887. Records and recent months use complete months only.
How does July in Decatur compare across Illinois?
Across the 144 places PlainClimate covers in Illinois, July normal highs run from 81°F in Barrington to 90°F in Belleville; Decatur's is 86°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.