Climate averages 1991–2020

Decatur weather
in January.

A cold month with moderate precipitation: the coolest and the 3rd driest of the year.

Long-term climate patterns, not a forecast for a particular trip.

Average high 1.8°C Daytime mean, January

Average low -6.3°C Night-time mean, January

Precipitation 69 mm 9 days with ≥1 mm

Daylight 10 h Sunrise to sunset, per day

January is a cold month in Decatur: daytime highs average 1.8°C and nights cool to about -6.3°C. By daytime temperature it is the coolest month of the year.

Expect about 69 mm of precipitation on roughly 9 days, which makes January a month with moderate precipitation (the 3rd driest of the 12 months). Daylight, from sunrise to sunset, lasts about 9 h 42 min on an average January day.

The nearest other city in this atlas is Springfield (Illinois), United States (59 km away). In January its highs average 1.9°C, about as warm as Decatur, with 61 mm of precipitation.

Among the 498 cities listed in the United States, Decatur ranks 399th of 498 for the warmest January highs and joint 216th of 498 for the driest January (precipitation, lowest first). The mean January high of those 498 cities is 9.5°C; Decatur is 7.6°C cooler than that mean.

From January to February, average highs rise by 2.8°C to 4.6°C, and monthly precipitation falls from 69 mm to 59 mm.

The annual picture

January in context

30-year average

Average highAverage low°C

Monthly precipitation

Average total · mm

Averages 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

1991–2020

Monthly climate averages for Decatur, 1991–2020
Month	Average highHigh / low	Average low	Precipitation mm/month	Wet days ≥1 mm/day	Daylight hours/dayDaylight h/day
January, selected	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	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

January in nearby cities

Distance from Decatur

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 limits

How 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.