Decatur weather in January: Decatur, Illinois: normal highs, lows, rain and records for January
Decatur in January has a normal high of 35°F and a normal low of 20°F, a daily mean of 27°F, holding near 35°F all month. Measurable precipitation falls on 8 days in a normal January, 1.99 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 2°C and low of −7°C, 51 mm of precipitation in January.
- 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 January?
The normal high is 35°F and the normal low 20°F, for a daily mean of 27.4°F. January is 5.0°F cooler than December and 4.2°F cooler than February. January is the 12th warmest month of the year in Decatur and the 11th wettest. From one year to the next January's mean temperature typically moves about 4.6°F either way (NOAA's standard deviation), so roughly two Januarys in three average between 23°F and 32°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 28%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| January 1 | 36°F | 22°F | 28% | 15% |
| January 8 | 35°F | 21°F | 27% | 14% |
| January 15 | 34°F | 20°F | 26% | 13% |
| January 22 | 34°F | 20°F | 25% | 12% |
| January 31 | 36°F | 20°F | 25% | 12% |
Every day of January: normal high, low and chance of precipitation (warmest afternoon January 1, coldest night January 19)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| January 1 | 36°F | 22°F | 28% | 15% | 9 h 20 min |
| January 2 | 36°F | 22°F | 27% | 14% | 9 h 20 min |
| January 3 | 35°F | 21°F | 27% | 14% | 9 h 30 min |
| January 4 | 35°F | 21°F | 27% | 14% | 9 h 30 min |
| January 5 | 35°F | 21°F | 27% | 14% | 9 h 30 min |
| January 6 | 35°F | 21°F | 27% | 14% | 9 h 30 min |
| January 7 | 35°F | 21°F | 27% | 14% | 9 h 30 min |
| January 8 | 35°F | 21°F | 27% | 14% | 9 h 30 min |
| January 9 | 35°F | 20°F | 27% | 14% | 9 h 30 min |
| January 10 | 35°F | 20°F | 27% | 14% | 9 h 30 min |
| January 11 | 34°F | 20°F | 27% | 14% | 9 h 30 min |
| January 12 | 34°F | 20°F | 26% | 13% | 9 h 30 min |
| January 13 | 34°F | 20°F | 26% | 13% | 9 h 40 min |
| January 14 | 34°F | 20°F | 26% | 13% | 9 h 40 min |
| January 15 | 34°F | 20°F | 26% | 13% | 9 h 40 min |
| January 16 | 34°F | 20°F | 26% | 13% | 9 h 40 min |
| January 17 | 34°F | 20°F | 25% | 13% | 9 h 40 min |
| January 18 | 34°F | 20°F | 25% | 13% | 9 h 40 min |
| January 19 | 34°F | 20°F | 25% | 13% | 9 h 40 min |
| January 20 | 34°F | 20°F | 25% | 12% | 9 h 50 min |
| January 21 | 34°F | 20°F | 25% | 12% | 9 h 50 min |
| January 22 | 34°F | 20°F | 25% | 12% | 9 h 50 min |
| January 23 | 34°F | 20°F | 25% | 12% | 9 h 50 min |
| January 24 | 35°F | 20°F | 25% | 12% | 9 h 50 min |
| January 25 | 35°F | 20°F | 25% | 12% | 9 h 50 min |
| January 26 | 35°F | 20°F | 25% | 12% | 10 h |
| January 27 | 35°F | 20°F | 25% | 12% | 10 h |
| January 28 | 35°F | 20°F | 25% | 12% | 10 h |
| January 29 | 35°F | 20°F | 25% | 12% | 10 h |
| January 30 | 35°F | 20°F | 25% | 12% | 10 h |
| January 31 | 36°F | 20°F | 25% | 12% | 10 h 10 min |
- Normal high
- 35°FJanuary average
- Normal low
- 20°FJanuary average
- Precipitation
- 1.99 inmonth total
- Days with precipitation
- 80.01 inch or more
- Nights at 32°F or colder
- 27
- Daylight
- 9 h 20 min to 10 h 10 minJanuary 1 to January 31
- Sunshine
- 62%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 January?
On a given January day the chance of 0.01 inch or more is 26% on average, highest around January 1 (28%). In all, 1.99 in falls on 8 days of a normal January, 1 of them with an inch or more.
In a normal January in Decatur, 27 nights fall to freezing and 12 days stay below freezing all day.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00003887.
How humid and windy is Decatur in January?
At 3 p.m. the normal temperature is 34°F with 65% relative humidity and a dew point of 23°F; at 6 a.m. it is 25°F with 81% humidity. The wind averages 11.2 mph, most often from the west in the afternoon. A dew point under 50°F feels dry.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 25°F | 20°F | 81% | 10.3 mph | 54% |
| 9 a.m. | 27°F | 21°F | 78% | 11.7 mph | 50% |
| noon | 32°F | 23°F | 68% | 12.6 mph | 49% |
| 3 p.m. | 34°F | 23°F | 65% | 12.7 mph | 48% |
| 6 p.m. | 31°F | 23°F | 73% | 10.5 mph | 48% |
| 9 p.m. | 28°F | 22°F | 77% | 10.7 mph | 54% |
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 January in Decatur?
The warmest January temperature on this station's record (since 2000) is 68°F, on January 7, 2008; the coldest is −16°F, on January 30, 2019. The wettest January brought 5.96 in (2005).
The January mean against the 1991-2020 normal of 27.4°F: 2021 29.3°F (+1.9), 2022 23.7°F (−3.7), 2023 36.1°F (+8.7), 2024 27.4°F (at normal), 2025 23.8°F (−3.6), 2026 25.1°F (−2.3). 2 of 6 ran warmer than normal.
| January | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 29.3°F | +1.9°F | 3.36 in |
| 2022 | 23.7°F | −3.7°F | 0.51 in |
| 2023 | 36.1°F | +8.7°F | 1.73 in |
| 2024 | 27.4°F | at normal | 4.55 in |
| 2025 | 23.8°F | −3.6°F | 0.21 in |
| 2026 | 25.1°F | −2.3°F | 0.29 in |
Source: records: ACIS, station USW00003887; recent months: ACIS, station USW00003887. Records and recent months use complete months only.
How does January in Decatur compare across Illinois?
Across the 144 places PlainClimate covers in Illinois, January normal highs run from 27°F in Galena to 45°F in Anna; Decatur's is 35°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.