Mount Vernon weather in January

In January, Mount Vernon sees average daytime highs of 41°F and overnight lows near 26°F, with 3.3 in of precipitation across 9 wet days and about 9.6 hours of daylight. It is the 12th-warmest and 8th-wettest month of the year here.

Day-to-day highs hold fairly steady near 41°F through the month. The sky is clear or mostly clear about 29% of the time in January, and the air most often feels dry.

Daylight stretches from about 9 h 24 min at the start of January to 10 hours by month's end. Set against the rest of the year, January is Mount Vernon's 10th-clearest and 3rd-windiest month. For the whole year in context, see Mount Vernon's year-round climate.

Daytime high
41°
12th warmest
Overnight low
26°
1st coldest
Precipitation
3.3 in
9 wet days
Daylight
9 h 36 min
7:17 AM – 4:53 PM
Cloud cover
64%
10th clearest
Wind
8 mph
3rd windiest
Solar energy
2.21 kWh/m²
Travel score
0.0
out of 10

Mount Vernon is city located near the center of Jefferson County, Illinois, United States.

Density
396/km²
people per km²
Founded
1817

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 41°F through the month.

A typical January day in Mount Vernon reaches about 41°F in the afternoon and slips back to 26°F overnight — a 14°F spread between the day's warmth and the night's chill. On most days the high lands between 26°F and 57°F. Set against its neighbours, January runs about 4°F cooler than December and about 5°F cooler than February.

20°40°60°151015202531
Avg high (°F)Avg low (°F)
14228
24128
34128
44127
54127
64127
74127
84127
94027
104026
114026
124026
134026
144026
154026
164026
174026
184026
194026
204026
214026
224026
234026
244126
254126
264126
274126
284126
294227
304227
314227

How January really feels in Mount Vernon

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
wind chill below the day's low

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

Mount Vernon weather by month

How January compares with the rest of the year at a glance. January is the 12th-warmest and 8th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan41° / 26°3.392.69.60.0
Feb45° / 30°2.98.42.710.51.1
Mar56° / 38°4.110.81.211.73.7
Apr67° / 49°5.211.30.1135.9
May76° / 59°5.112.90146.3
Jun85° / 68°3.910.4014.65.2
Jul88° / 71°3.410.3014.44.5
Aug86° / 69°2.88.4013.55.2
Sep80° / 61°3.07.3012.37.0
Oct68° / 49°3.67.90116.8
Nov55° / 39°3.88.80.69.93.6
Dec44° / 31°3.28.629.40.9

Cloud cover in January

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 29% of the time in January.

Beyond those clear spells, partly cloudy skies cover about 11% of January, with mostly cloudy or overcast conditions the remaining 60%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
13664
23763
33763
43763
53763
63763
73862
83862
93862
103862
113961
123961
134060
143961
153961
164060
174060
184060
194159
204159
214258
224258
234357
244357
254456
264456
274456
284357
294357
304357
314258

Chance of precipitation in January

Any precipitationSnow

Mount Vernon gets around 3.3 in of rain and snow over 9 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 29% and peaks near 32% on the wettest days, and about 3 days bring snow.

0%10%20%30%40%151015202531
Rain chance (%)Snow chance (%)
1288
2298
3308
4308
5318
6318
7328
8329
9329
10329
11319
12319
13319
14319
15309
16309
17299
18289
19289
20279
21279
22269
23269
24269
25269
26269
27269
28269
29269
30269
31269

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 99% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)
1973
2973
3973
4973
5973
6973
7973
8973
9982
10982
11982
12982
13991
14991
15991
16991
17991
18991
191000
201000
211000
221000
231000
241000
251000
26991
27991
28991
29991
30991
31991

Wind in January

Winds average 8 mph in January.

Across January, daily wind ranges from about 8 mph on the calmest days to 8 mph at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (mph)Feels
18light breeze
28light breeze
38light breeze
48light breeze
58light breeze
68light breeze
78light breeze
88light breeze
98light breeze
108light breeze
118light breeze
128light breeze
138light breeze
148light breeze
158light breeze
168light breeze
178light breeze
188light breeze
198light breeze
208light breeze
218light breeze
228light breeze
238light breeze
248light breeze
258light breeze
268light breeze
278light breeze
288light breeze
298light breeze
308light breeze
318light breeze

Sunrise & sunset in January

DaylightNight

Daylight runs from about 9 h 24 min at the start of January to 10 hours by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 36 minutes over January. Sunrise moves from 7:18 AM to 7:09 AM, and sunset from 4:40 PM to 5:09 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
19.47:184:40
29.47:184:41
39.47:184:42
49.47:184:42
59.47:184:43
69.47:184:44
79.47:184:45
89.57:184:46
99.57:184:46
109.57:184:47
119.57:184:48
129.57:184:49
139.57:174:50
149.67:174:51
159.67:174:52
169.67:174:53
179.67:164:54
189.77:164:55
199.77:164:56
209.77:154:57
219.77:154:58
229.77:144:59
239.87:145:00
249.87:135:01
259.87:135:02
269.97:125:04
279.97:125:05
289.97:115:06
299.97:105:07
3010.07:105:08
3110.07:095:09

Solar energy in January

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in January, about 2.21 kWh/m².

For context, solar energy here swings from a low near 1.9 kWh/m² to a high of 6.46 kWh/m² in June across the year — January's 2.21 kWh/m² sits near the bottom.

0123151015202531
Solar energy (kWh/m²)Level
11.9Dim
21.9Dim
31.9Dim
42.0Dim
52.0Dim
62.0Dim
72.0Moderate
82.0Moderate
92.0Moderate
102.0Moderate
112.1Moderate
122.1Moderate
132.1Moderate
142.1Moderate
152.2Moderate
162.2Moderate
172.2Moderate
182.3Moderate
192.3Moderate
202.3Moderate
212.4Moderate
222.4Moderate
232.4Moderate
242.4Moderate
252.5Moderate
262.5Moderate
272.5Moderate
282.6Moderate
292.6Moderate
302.6Moderate
312.6Moderate
Planning a trip in January

Is January a good time to visit Mount Vernon?

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 Mount Vernon.

What to pack for Mount Vernon in January

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

In January, Mount Vernon sees daytime highs around 41°F and nights near 26°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 Mount Vernon 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 Mount Vernon peaks around July 10 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJul 10UV 9Dec 23UV 2
UV index (midday)Level
Jan2Moderate
Feb3Moderate
Mar5High
Apr7High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep7High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Mount Vernon 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 Mount Vernon is worst in July — around 18 µg/m³ PM2.5 (moderate), about 2.4× the cleanest month (October, 8 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1417 µg/m³Oct 238 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb11Good
Mar12Good
Apr11Good
May14Moderate
Jun16Moderate
Jul18Moderate
Aug14Moderate
Sep11Good
Oct8Good
Nov8Good
Dec9Good
Location & terrain

Where is Mount Vernon?

Mount Vernon sits at 38.3°N, 88.9°W, 512 ft above sea level, in United States. The nearest listed city is Marion, 40 mi away.

Topography around Mount Vernon

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

Within 2 miles, the terrain around Mount Vernon has only modest variations in elevation — a maximum elevation change of 174 ft around an average of 489 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 279 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 499 ft.

The land around Mount Vernon is covered by trees (49%) within 2 miles, trees (42%) and cropland (37%) within 10 miles, and cropland (59%) and trees (31%) within 50 miles.

2 miles
174 ft
10 miles
279 ft
50 miles
499 ft
treesgrasslandcroplandartificial surfaceswater
January weather nearby: Marion 40 mi · Carbondale 44 mi · O'Fallon 58 mi · Belleville 60 mi · Fairview Heights 62 mi · Collinsville 63 mi · Edwardsville 66 mi · East Saint Louis 71 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 Mount Vernon (38.3173°, -88.9031°, elevation 512 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. 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).