Decatur weather in January

In January, Decatur sees average daytime highs of 36°F and overnight lows near 21°F, with 2.7 in of precipitation across 8.5 wet days and about 9.5 hours of daylight. It is the 12th-warmest and 10th-wettest month of the year here.

Day-to-day highs hold fairly steady near 36°F through the month. The sky is clear or mostly clear about 25% of the time in January, and the air most often feels dry.

Daylight stretches from about 9 h 12 min at the start of January to 9 h 54 min by month's end. Set against the rest of the year, January is Decatur's 12th-clearest and 2nd-windiest month. For the whole year in context, see Decatur's year-round climate.

Daytime high
36°
12th warmest
Overnight low
21°
1st coldest
Precipitation
2.7 in
8.5 wet days
Daylight
9 h 30 min
7:21 AM – 4:49 PM
Cloud cover
68%
12th clearest
Wind
10 mph
2nd windiest
Solar energy
2.08 kWh/m²
Travel score
0.0
out of 10

Decatur is city in Macon County, Illinois, United States.

Density
602/km²
people per km²
Founded
1823

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in January

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 36°F through the month.

A typical January day in Decatur reaches about 36°F in the afternoon and slips back to 21°F overnight — a 15°F spread between the day's warmth and the night's chill. On most days the high lands between 20°F and 52°F. Set against its neighbours, January runs about 4°F cooler than December and about 4°F cooler than February.

20°40°60°151015202531
Avg high (°F)Avg low (°F)
13723
23723
33723
43723
53622
63622
73622
83622
93622
103621
113621
123521
133521
143521
153521
163520
173520
183520
193520
203520
213520
223520
233520
243520
253620
263621
273621
283621
293621
303621
313721

How January really feels in Decatur

Once humidity and wind are folded in, January averages 0 days that feel above 90°F and 31 that feel at or below 32°F — the comfort signal a plain temperature reading hides.

Days feeling ≥ 90°F
0
heat index over the day's high
Days feeling ≤ 32°F
31
31 feel bitter (≤ 14°F)

The story in January is cold — wind chill drags the overnight "feels like" below the raw low.

Decatur weather by month

How January compares with the rest of the year at a glance. January is the 12th-warmest and 10th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan36° / 21°2.78.549.50.0
Feb40° / 24°2.37.53.410.40.2
Mar52° / 34°3.39.71.511.72.7
Apr64° / 44°4.611.80.3135.3
May73° / 55°4.813.2014.26.2
Jun82° / 64°4.310.9014.86.0
Jul84° / 67°3.610.3014.55.5
Aug83° / 65°3.08.5013.66.1
Sep78° / 57°3.27.4012.37.3
Oct65° / 46°3.58.60.110.96.2
Nov51° / 35°3.58.70.89.82.7
Dec40° / 26°2.58.72.99.20.2

Cloud cover in January

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 25% of the time in January, the cloudiest month of the year.

Beyond those clear spells, partly cloudy skies cover about 11% of January, with mostly cloudy or overcast conditions the remaining 65%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
13466
23466
33466
43367
53367
63367
73367
83367
93367
103367
113367
123466
133466
143466
153466
163565
173565
183565
193565
203763
213763
223763
233763
243763
253763
263763
273763
283862
293862
303862
313862

Chance of precipitation in January

Any precipitationSnow

Decatur gets around 2.7 in of rain and snow over 8.5 wet days in January. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 27% and peaks near 29% on the wettest days, and about 4 days bring snow.

0%10%20%30%40%151015202531
Rain chance (%)Snow chance (%)
12710
22811
32811
42811
52911
62912
72912
82912
92912
102913
112913
122913
132913
142913
152913
162913
172813
182813
192713
202713
212714
222614
232614
242614
252514
262514
272514
282514
292514
302514
312514

Humidity in January

DryComfortableHumidMuggyOppressiveMiserable

Most of January feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, January lands in the dry band about 100% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)
1991
2991
3991
4991
5991
6991
7991
81000
91000
101000
111000
121000
131000
141000
151000
161000
171000
181000
191000
201000
211000
221000
231000
241000
251000
261000
271000
281000
291000
301000
311000

Wind in January

Winds average 10 mph in January.

Across January, daily wind ranges from about 9 mph on the calmest days to 10 mph at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (mph)Feels
19light breeze
210light breeze
310light breeze
410light breeze
510light breeze
610light breeze
710light breeze
810light breeze
910light breeze
1010light breeze
1110light breeze
1210light breeze
1310light breeze
1410light breeze
1510light breeze
1610light breeze
1710light breeze
1810light breeze
1910light breeze
209light breeze
219light breeze
229light breeze
239light breeze
249light breeze
259light breeze
269light breeze
279light breeze
289light breeze
299light breeze
309light breeze
319light breeze

Sunrise & sunset in January

DaylightNight

Daylight runs from about 9 h 12 min at the start of January to 9 h 54 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 42 minutes over January. Sunrise moves from 7:22 AM to 7:12 AM, and sunset from 4:36 PM to 5:06 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
19.27:224:36
29.27:224:36
39.27:234:37
49.37:234:38
59.37:234:39
69.37:234:40
79.37:234:40
89.37:234:41
99.37:234:42
109.37:224:43
119.47:224:44
129.47:224:45
139.47:224:46
149.47:224:47
159.47:214:48
169.57:214:49
179.57:214:50
189.57:204:51
199.57:204:52
209.67:194:53
219.67:194:54
229.67:184:56
239.67:184:57
249.77:174:58
259.77:174:59
269.77:165:00
279.87:155:01
289.87:155:02
299.87:145:04
309.97:135:05
319.97:125:06

Solar energy in January

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in January, about 2.08 kWh/m².

For context, solar energy here swings from a low near 1.8 kWh/m² to a high of 6.44 kWh/m² in June across the year — January's 2.08 kWh/m² sits near the bottom.

0123151015202531
Solar energy (kWh/m²)Level
11.8Dim
21.8Dim
31.9Dim
41.9Dim
51.9Dim
61.9Dim
71.9Dim
81.9Dim
91.9Dim
101.9Dim
112.0Dim
122.0Dim
132.0Moderate
142.0Moderate
152.0Moderate
162.1Moderate
172.1Moderate
182.1Moderate
192.1Moderate
202.2Moderate
212.2Moderate
222.2Moderate
232.3Moderate
242.3Moderate
252.3Moderate
262.4Moderate
272.4Moderate
282.4Moderate
292.5Moderate
302.5Moderate
312.5Moderate
Planning a trip in January

Hazard calendar for Decatur

In seasonPeak

None of Decatur's seasonal hazards are active in January. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

Decatur sits in the Atlantic hurricane belt; the season peaks August–October.

Atlantic hurricane
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is January a good time to visit Decatur?

Our two travel scores rate January for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

0.0
Sightseeing
12th-best month of the year
0.0
Beach & pool
10th-best month of the year

January is a weaker month for outdoor sightseeing in Decatur.

What to pack for Decatur in January

From January's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In January, Decatur sees daytime highs around 36°F and nights near 21°F. Pack a warm layer and a heavy coat. Worth having: rain gear. About 9 days see rain.

a warm layera heavy coatrain gear

UV index in Decatur in January

LowModerateHighVery highExtreme

Clear-sky midday UV in January peaks around 2. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Decatur peaks around June 22 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near January 1 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJun 22UV 9Jan 1UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep6High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Decatur in January

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where January falls, not just the annual average.

Air quality in Decatur is worst in July — around 17 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (October, 8 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodModerateGoodJul 1716 µg/m³Oct 228 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb13Moderate
Mar12Moderate
Apr11Good
May14Moderate
Jun14Moderate
Jul17Moderate
Aug15Moderate
Sep12Good
Oct8Good
Nov8Good
Dec9Good
Location & terrain

Where is Decatur?

Decatur sits at 39.8°N, 89.0°W, 673 ft above sea level, in United States. The nearest listed city is Springfield, 37 mi away.

Topography around Decatur

How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Decatur.

Within 2 miles, the terrain around Decatur has only modest variations in elevation — a maximum elevation change of 164 ft around an average of 666 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 197 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 489 ft.

The land around Decatur is covered by trees (43%) and artificial surfaces (34%) within 2 miles, cropland (68%) within 10 miles, and cropland (83%) within 50 miles.

2 miles
164 ft
10 miles
197 ft
50 miles
489 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
January weather nearby: Springfield 37 mi · Mattoon 40 mi · Champaign 42 mi · Urbana 43 mi · Bloomington 45 mi · Normal 47 mi · Charleston 48 mi · Morton 60 mi

United States travel facts

Power plugs
Type A / B
120 V · 60 Hz
Prices
≈ 100% of US
price level, 2025
GDP per capita
$90,027
2025
Happiness
6.8 / 10
World Happiness, 2025
Safe drinking water
98%
of population, 2024
Homicide rate
5.8
per 100k, 2023
Road deaths
12.7
per 100k/yr, 2019
Income group
High
World Bank
Religion
Protestant 47%unaffiliated 23%Roman Catholic 21%Jewish 2%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Decatur (39.8403°, -88.9548°, elevation 673 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).