Thornton weather in January

In January, Thornton sees average daytime highs of 42°F and overnight lows near 18°F, with 0.9 in of precipitation across 5.2 wet days and about 9.5 hours of daylight. It is the 11th-warmest and 11th-wettest month of the year here.

Day-to-day highs hold fairly steady near 42°F through the month. The sky is clear or mostly clear about 50% 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 Thornton's 5th-clearest and 4th-windiest month. For the whole year in context, see Thornton's year-round climate.

Daytime high: 42°; 11th warmest
Overnight low: 18°; 1st coldest
Precipitation: 0.9 in; 5.2 wet days
Daylight: 9 h 30 min; 7:25 AM – 4:53 PM
Cloud cover: 44%; 5th clearest
Wind: 5 mph; 4th windiest
Solar energy: 2.86 kWh/m²
Travel score: 0.3; out of 10

Thornton is city in Adams and Weld counties in Colorado, United States.

Density: 1,433/km²; people per km²
Founded: 1956

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

← December Thornton year-round climate February →Best places to visit in January

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

Temperature in January

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 42°F through the month.

A typical January day in Thornton reaches about 42°F in the afternoon and slips back to 18°F overnight — a 24°F spread between the day's warmth and the night's chill. On most days the high lands between 27°F and 56°F. Set against its neighbours, January runs on par with December and about 3°F cooler than February.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31
Avg high (°F)	40	40	40	40	41	41	41	41	41	41	41	42	42	42	42	42	42	42	42	43	43	43	43	43	43	43	43	42	42	42	42
Avg low (°F)	17	17	17	17	17	17	17	17	17	18	18	18	18	18	18	18	19	19	19	19	19	19	19	19	19	19	19	19	19	19	19

	Avg high (°F)	Avg low (°F)
1	40	17
2	40	17
3	40	17
4	40	17
5	41	17
6	41	17
7	41	17
8	41	17
9	41	17
10	41	18
11	41	18
12	42	18
13	42	18
14	42	18
15	42	18
16	42	18
17	42	19
18	42	19
19	42	19
20	43	19
21	43	19
22	43	19
23	43	19
24	43	19
25	43	19
26	43	19
27	43	19
28	42	19
29	42	19
30	42	19
31	42	19

How January really feels in Thornton

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

heat index over the day's high

Days feeling ≤ 32°F

31 feel bitter (≤ 14°F)

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

Thornton weather by month

How January compares with the rest of the year at a glance. January is the 11th-warmest and 11th-wettest month here — the current month is highlighted below.

Month	High / Low (°F)	Rainfall (inches)	Wet days	Snow days	Daylight (hours)	Travel score
Jan	42° / 18°	0.9	5.2	5	9.5	0.3
Feb	44° / 20°	0.9	5.8	5.5	10.4	1.0
Mar	53° / 27°	1.9	7.6	5.7	11.7	3.3
Apr	59° / 33°	2.7	9.9	4.7	13	4.7
May	69° / 43°	3.2	11	1	14.2	6.2
Jun	80° / 52°	2.1	8.3	0	14.8	6.8
Jul	85° / 58°	1.6	7.2	0	14.5	5.5
Aug	83° / 57°	1.5	6.4	0	13.6	6.3
Sep	76° / 49°	1.4	5.8	0.5	12.3	7.7
Oct	64° / 37°	1.6	6.1	2.2	10.9	6.4
Nov	51° / 26°	1.2	6	5.1	9.8	2.9
Dec	42° / 18°	0.8	4.8	4.9	9.2	0.3

Cloud cover in January

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 50% of the time in January.

Beyond those clear spells, partly cloudy skies cover about 15% of January, with mostly cloudy or overcast conditions the remaining 35%.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31
Clearer (%)	69	69	68	68	67	67	67	66	67	66	66	65	66	66	65	66	66	66	64	64	65	64	64	63	63	62	62	62	61	61	60
Cloudier (%)	31	31	32	32	33	33	33	34	33	34	34	35	34	34	35	34	34	34	36	36	35	36	36	37	37	38	38	38	39	39	40

	Clearer (%)	Cloudier (%)
1	69	31
2	69	31
3	68	32
4	68	32
5	67	33
6	67	33
7	67	33
8	66	34
9	67	33
10	66	34
11	66	34
12	65	35
13	66	34
14	66	34
15	65	35
16	66	34
17	66	34
18	66	34
19	64	36
20	64	36
21	65	35
22	64	36
23	64	36
24	63	37
25	63	37
26	62	38
27	62	38
28	62	38
29	61	39
30	61	39
31	60	40

Chance of precipitation in January

Any precipitationSnow

Thornton gets around 0.9 in of rain and snow over 5.2 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 16% and peaks near 21% on the wettest days, and about 5 days bring snow.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31
Rain chance (%)	15	15	15	15	15	15	15	15	15	15	15	14	14	14	14	14	14	14	14	15	15	16	16	17	18	18	19	20	20	21	21
Snow chance (%)	15	15	15	15	15	15	15	15	15	15	15	15	14	14	14	14	14	14	14	14	15	15	16	16	17	18	18	19	19	20	20

	Rain chance (%)	Snow chance (%)
1	15	15
2	15	15
3	15	15
4	15	15
5	15	15
6	15	15
7	15	15
8	15	15
9	15	15
10	15	15
11	15	15
12	14	15
13	14	14
14	14	14
15	14	14
16	14	14
17	14	14
18	14	14
19	14	14
20	15	14
21	15	15
22	16	15
23	16	16
24	17	16
25	18	17
26	18	18
27	19	18
28	20	19
29	20	19
30	21	20
31	21	20

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.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31
Dry (%)	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100	100

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100
31	100

Wind in January

Winds average 5 mph in January.

Across January, daily wind ranges from about 5 mph on the calmest days to 5 mph at its breeziest. It stays fairly steady from day to day.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31
Wind speed (mph)	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5	5
Feels	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm

	Wind speed (mph)	Feels
1	5	calm
2	5	calm
3	5	calm
4	5	calm
5	5	calm
6	5	calm
7	5	calm
8	5	calm
9	5	calm
10	5	calm
11	5	calm
12	5	calm
13	5	calm
14	5	calm
15	5	calm
16	5	calm
17	5	calm
18	5	calm
19	5	calm
20	5	calm
21	5	calm
22	5	calm
23	5	calm
24	5	calm
25	5	calm
26	5	calm
27	5	calm
28	5	calm
29	5	calm
30	5	calm
31	5	calm

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 7:26 AM to 7:17 AM, and sunset from 4:40 PM to 5:10 PM.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31
Daylight (h)	9.2	9.2	9.2	9.3	9.3	9.3	9.3	9.3	9.3	9.3	9.4	9.4	9.4	9.4	9.4	9.5	9.5	9.5	9.5	9.6	9.6	9.6	9.6	9.7	9.7	9.7	9.8	9.8	9.8	9.9	9.9
Sunrise (AM)	7:26	7:27	7:27	7:27	7:27	7:27	7:27	7:27	7:27	7:27	7:26	7:26	7:26	7:26	7:26	7:25	7:25	7:24	7:24	7:24	7:23	7:23	7:22	7:21	7:21	7:20	7:20	7:19	7:18	7:17	7:17
Sunset (PM)	4:40	4:40	4:41	4:42	4:43	4:44	4:44	4:45	4:46	4:47	4:48	4:49	4:50	4:51	4:52	4:53	4:54	4:55	4:56	4:57	4:58	5:00	5:01	5:02	5:03	5:04	5:05	5:06	5:08	5:09	5:10

	Daylight (h)	Sunrise (AM)	Sunset (PM)
1	9.2	7:26	4:40
2	9.2	7:27	4:40
3	9.2	7:27	4:41
4	9.3	7:27	4:42
5	9.3	7:27	4:43
6	9.3	7:27	4:44
7	9.3	7:27	4:44
8	9.3	7:27	4:45
9	9.3	7:27	4:46
10	9.3	7:27	4:47
11	9.4	7:26	4:48
12	9.4	7:26	4:49
13	9.4	7:26	4:50
14	9.4	7:26	4:51
15	9.4	7:26	4:52
16	9.5	7:25	4:53
17	9.5	7:25	4:54
18	9.5	7:24	4:55
19	9.5	7:24	4:56
20	9.6	7:24	4:57
21	9.6	7:23	4:58
22	9.6	7:23	5:00
23	9.6	7:22	5:01
24	9.7	7:21	5:02
25	9.7	7:21	5:03
26	9.7	7:20	5:04
27	9.8	7:20	5:05
28	9.8	7:19	5:06
29	9.8	7:18	5:08
30	9.9	7:17	5:09
31	9.9	7:17	5:10

Solar energy in January

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in January, about 2.86 kWh/m².

For context, solar energy here swings from a low near 2.55 kWh/m² to a high of 7.45 kWh/m² in June across the year — January's 2.86 kWh/m² sits near the bottom.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31
Solar energy (kWh/m²)	2.6	2.6	2.7	2.7	2.7	2.7	2.7	2.7	2.7	2.7	2.8	2.8	2.8	2.8	2.8	2.9	2.9	2.9	2.9	3.0	3.0	3.0	3.0	3.1	3.1	3.1	3.2	3.2	3.2	3.3	3.3
Level	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate

	Solar energy (kWh/m²)	Level
1	2.6	Moderate
2	2.6	Moderate
3	2.7	Moderate
4	2.7	Moderate
5	2.7	Moderate
6	2.7	Moderate
7	2.7	Moderate
8	2.7	Moderate
9	2.7	Moderate
10	2.7	Moderate
11	2.8	Moderate
12	2.8	Moderate
13	2.8	Moderate
14	2.8	Moderate
15	2.8	Moderate
16	2.9	Moderate
17	2.9	Moderate
18	2.9	Moderate
19	2.9	Moderate
20	3.0	Moderate
21	3.0	Moderate
22	3.0	Moderate
23	3.0	Moderate
24	3.1	Moderate
25	3.1	Moderate
26	3.1	Moderate
27	3.2	Moderate
28	3.2	Moderate
29	3.2	Moderate
30	3.3	Moderate
31	3.3	Moderate

Planning a trip in January

Is January a good time to visit Thornton?

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

0.3

Sightseeing

11th-best month of the year

0.0

Beach & pool

10th-best month of the year

January is a weaker month for outdoor sightseeing in Thornton.

What to pack for Thornton in January

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

In January, Thornton sees daytime highs around 42°F and nights near 18°F. Pack a warm layer and a heavy coat. About 5 days see rain.

a warm layera heavy coat

UV index in Thornton 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 Thornton peaks around July 12 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (low).

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

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
UV index (midday)	2	4	7	6	7	10	11	10	7	5	3	2
Level	Low	Moderate	High	High	Very high	Extreme	Extreme	Very high	Very high	High	Moderate	Low

	UV index (midday)	Level
Jan	2	Low
Feb	4	Moderate
Mar	7	High
Apr	6	High
May	7	Very high
Jun	10	Extreme
Jul	11	Extreme
Aug	10	Very high
Sep	7	Very high
Oct	5	High
Nov	3	Moderate
Dec	2	Low

Air quality in Thornton 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 Thornton is worst in August — around 21 µg/m³ PM2.5 (moderate), about 1.6× the cleanest month (May, 13 µg/m³).

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

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
PM2.5 (µg/m³)	17	15	16	13	13	14	14	21	13	15	15	16
Level	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate

	PM2.5 (µg/m³)	Level
Jan	17	Moderate
Feb	15	Moderate
Mar	16	Moderate
Apr	13	Moderate
May	13	Moderate
Jun	14	Moderate
Jul	14	Moderate
Aug	21	Moderate
Sep	13	Moderate
Oct	15	Moderate
Nov	15	Moderate
Dec	16	Moderate

Location & terrain

Where is Thornton?

Thornton sits at 39.9°N, 105.0°W, 5,351 ft above sea level, in United States. The nearest listed city is Northglenn, 1.2 mi away.

Topography around Thornton

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

Within 2 miles, the terrain around Thornton has only modest variations in elevation — a maximum elevation change of 472 ft around an average of 5,276 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 856 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 9,708 ft.

The land around Thornton is covered by artificial surfaces (68%) within 2 miles, artificial surfaces (45%) and grassland (34%) within 10 miles, and grassland (43%) and trees (30%) within 50 miles.

2 miles

472 ft

artificial surfaces 68%

10 miles

856 ft

artificial surfaces 45%

50 miles

9,708 ft

grassland 43%

treesgrasslandcroplandartificial surfacesbare terrainwatermoss and lichen

← December Thornton year-round climate February →Best places to visit in January

January weather nearby: Northglenn 1.2 mi · Sherrelwood 2.5 mi · Westminster 4.3 mi · Commerce City 4.3 mi · Broomfield 6.8 mi · Arvada 7.5 mi · Denver 8.7 mi · Wheat Ridge 8.7 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

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 Thornton (39.868°, -104.9719°, elevation 5,351 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).

	Avg high (°F)	Avg low (°F)
1	40	17
2	40	17
3	40	17
4	40	17
5	41	17
6	41	17
7	41	17
8	41	17
9	41	17
10	41	18
11	41	18
12	42	18
13	42	18
14	42	18
15	42	18
16	42	18
17	42	19
18	42	19
19	42	19
20	43	19
21	43	19
22	43	19
23	43	19
24	43	19
25	43	19
26	43	19
27	43	19
28	42	19
29	42	19
30	42	19
31	42	19

	Clearer (%)	Cloudier (%)
1	69	31
2	69	31
3	68	32
4	68	32
5	67	33
6	67	33
7	67	33
8	66	34
9	67	33
10	66	34
11	66	34
12	65	35
13	66	34
14	66	34
15	65	35
16	66	34
17	66	34
18	66	34
19	64	36
20	64	36
21	65	35
22	64	36
23	64	36
24	63	37
25	63	37
26	62	38
27	62	38
28	62	38
29	61	39
30	61	39
31	60	40

	Rain chance (%)	Snow chance (%)
1	15	15
2	15	15
3	15	15
4	15	15
5	15	15
6	15	15
7	15	15
8	15	15
9	15	15
10	15	15
11	15	15
12	14	15
13	14	14
14	14	14
15	14	14
16	14	14
17	14	14
18	14	14
19	14	14
20	15	14
21	15	15
22	16	15
23	16	16
24	17	16
25	18	17
26	18	18
27	19	18
28	20	19
29	20	19
30	21	20
31	21	20

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100
31	100

	Avg high (°F)	Avg low (°F)
1	40	17
2	40	17
3	40	17
4	40	17
5	41	17
6	41	17
7	41	17
8	41	17
9	41	17
10	41	18
11	41	18
12	42	18
13	42	18
14	42	18
15	42	18
16	42	18
17	42	19
18	42	19
19	42	19
20	43	19
21	43	19
22	43	19
23	43	19
24	43	19
25	43	19
26	43	19
27	43	19
28	42	19
29	42	19
30	42	19
31	42	19

	Clearer (%)	Cloudier (%)
1	69	31
2	69	31
3	68	32
4	68	32
5	67	33
6	67	33
7	67	33
8	66	34
9	67	33
10	66	34
11	66	34
12	65	35
13	66	34
14	66	34
15	65	35
16	66	34
17	66	34
18	66	34
19	64	36
20	64	36
21	65	35
22	64	36
23	64	36
24	63	37
25	63	37
26	62	38
27	62	38
28	62	38
29	61	39
30	61	39
31	60	40

	Rain chance (%)	Snow chance (%)
1	15	15
2	15	15
3	15	15
4	15	15
5	15	15
6	15	15
7	15	15
8	15	15
9	15	15
10	15	15
11	15	15
12	14	15
13	14	14
14	14	14
15	14	14
16	14	14
17	14	14
18	14	14
19	14	14
20	15	14
21	15	15
22	16	15
23	16	16
24	17	16
25	18	17
26	18	18
27	19	18
28	20	19
29	20	19
30	21	20
31	21	20

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100
31	100

	Avg high (°F)	Avg low (°F)
1	40	17
2	40	17
3	40	17
4	40	17
5	41	17
6	41	17
7	41	17
8	41	17
9	41	17
10	41	18
11	41	18
12	42	18
13	42	18
14	42	18
15	42	18
16	42	18
17	42	19
18	42	19
19	42	19
20	43	19
21	43	19
22	43	19
23	43	19
24	43	19
25	43	19
26	43	19
27	43	19
28	42	19
29	42	19
30	42	19
31	42	19

	Clearer (%)	Cloudier (%)
1	69	31
2	69	31
3	68	32
4	68	32
5	67	33
6	67	33
7	67	33
8	66	34
9	67	33
10	66	34
11	66	34
12	65	35
13	66	34
14	66	34
15	65	35
16	66	34
17	66	34
18	66	34
19	64	36
20	64	36
21	65	35
22	64	36
23	64	36
24	63	37
25	63	37
26	62	38
27	62	38
28	62	38
29	61	39
30	61	39
31	60	40

	Rain chance (%)	Snow chance (%)
1	15	15
2	15	15
3	15	15
4	15	15
5	15	15
6	15	15
7	15	15
8	15	15
9	15	15
10	15	15
11	15	15
12	14	15
13	14	14
14	14	14
15	14	14
16	14	14
17	14	14
18	14	14
19	14	14
20	15	14
21	15	15
22	16	15
23	16	16
24	17	16
25	18	17
26	18	18
27	19	18
28	20	19
29	20	19
30	21	20
31	21	20

	Dry (%)
1	100
2	100
3	100
4	100
5	100
6	100
7	100
8	100
9	100
10	100
11	100
12	100
13	100
14	100
15	100
16	100
17	100
18	100
19	100
20	100
21	100
22	100
23	100
24	100
25	100
26	100
27	100
28	100
29	100
30	100
31	100