Boulder weather in January

In January, Boulder sees average daytime highs of 37°F and overnight lows near 14°F, with 0.9 in of precipitation across 5.7 wet days and about 9.5 hours of daylight. It is the 12th-warmest and 11th-wettest month of the year here.

Day-to-day highs hold fairly steady near 37°F through the month. The sky is clear or mostly clear about 47% 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 Boulder's 5th-clearest and 1st-windiest month. For the whole year in context, see Boulder's year-round climate.

Daytime high
37°
12th warmest
Overnight low
14°
1st coldest
Precipitation
0.9 in
5.7 wet days
Daylight
9 h 30 min
7:27 AM – 4:54 PM
Cloud cover
46%
5th clearest
Wind
6 mph
1st windiest
Solar energy
2.89 kWh/m²
Travel score
0.0
out of 10

Boulder is city in and county seat of Boulder County, Colorado, United States.

Density
1,606/km²
people per km²
Founded
1858

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 37°F through the month.

A typical January day in Boulder reaches about 37°F in the afternoon and slips back to 14°F overnight — a 23°F spread between the day's warmth and the night's chill. On most days the high lands between 24°F and 49°F. Set against its neighbours, January runs on par with December and about 3°F cooler than February.

20°40°60°151015202531
Avg high (°F)Avg low (°F)
13613
23613
33613
43613
53613
63614
73614
83614
93614
103714
113714
123714
133714
143714
153715
163715
173715
183715
193815
203815
213815
223815
233815
243815
253815
263815
273815
283815
293715
303715
313715

How January really feels in Boulder

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.

Boulder weather by month

How January compares with the rest of the year at a glance. January is the 12th-warmest and 11th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan37° / 14°0.95.75.59.50.0
Feb39° / 16°1.06.7710.40.0
Mar48° / 22°2.08.87.211.71.7
Apr54° / 29°3.111.17.9133.1
May63° / 38°4.014.93.514.24.8
Jun74° / 47°3.014.30.314.86.2
Jul80° / 53°3.014.8014.56.0
Aug78° / 52°2.814.9013.66.2
Sep71° / 44°2.19.70.912.36.8
Oct58° / 33°1.97.43.910.94.9
Nov46° / 22°1.36.45.79.81.4
Dec37° / 15°0.95.35.49.20.0

Cloud cover in January

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 47% of the time in January.

Beyond those clear spells, partly cloudy skies cover about 17% of January, with mostly cloudy or overcast conditions the remaining 36%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
16832
26733
36733
46634
56634
66535
76436
86436
96337
106436
116337
126337
136436
146436
156436
166535
176535
186535
196436
206436
216436
226337
236436
246337
256238
266238
276238
286139
296040
306040
315941

Chance of precipitation in January

Any precipitationSnow

Boulder gets around 0.9 in of rain and snow over 5.7 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 18% and peaks near 22% on the wettest days, and about 6 days bring snow.

0%10%20%30%151015202531
Rain chance (%)Snow chance (%)
11616
21616
31716
41716
51717
61717
71717
81717
91717
101717
111717
121717
131717
141716
151716
161716
171716
181716
191716
201717
211717
221817
231818
241918
251919
262019
272020
282120
292121
302121
312222

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 (%)
1100
2100
3100
4100
5100
6100
7100
8100
9100
10100
11100
12100
13100
14100
15100
16100
17100
18100
19100
20100
21100
22100
23100
24100
25100
26100
27100
28100
29100
30100
31100

Wind in January

Winds average 6 mph in January, the windiest month of the year.

Across January, daily wind ranges from about 5 mph on the calmest days to 6 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (mph)Feels
16calm
26calm
36calm
46calm
56calm
66calm
76calm
86calm
96calm
106calm
116calm
126calm
136calm
146calm
156calm
166calm
176calm
186calm
196calm
206calm
216calm
226calm
236calm
246calm
256calm
266calm
276calm
286calm
295calm
305calm
315calm

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 7:28 AM to 7:18 AM, and sunset from 4:40 PM to 5:11 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
19.27:284:40
29.27:284:41
39.27:284:42
49.27:284:43
59.27:294:44
69.37:294:44
79.37:294:45
89.37:284:46
99.37:284:47
109.37:284:48
119.37:284:49
129.47:284:50
139.47:284:51
149.47:274:52
159.47:274:53
169.57:274:54
179.57:264:55
189.57:264:56
199.57:264:57
209.67:254:58
219.67:254:59
229.67:245:00
239.67:245:02
249.77:235:03
259.77:225:04
269.77:225:05
279.77:215:06
289.87:205:07
299.87:205:08
309.87:195:10
319.97:185:11

Solar energy in January

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in January, about 2.89 kWh/m².

For context, solar energy here swings from a low near 2.56 kWh/m² to a high of 7.49 kWh/m² in June across the year — January's 2.89 kWh/m² sits near the bottom.

01234151015202531
Solar energy (kWh/m²)Level
12.7Moderate
22.7Moderate
32.7Moderate
42.7Moderate
52.7Moderate
62.7Moderate
72.7Moderate
82.7Moderate
92.8Moderate
102.8Moderate
112.8Moderate
122.8Moderate
132.8Moderate
142.8Moderate
152.9Moderate
162.9Moderate
172.9Moderate
182.9Moderate
193.0Moderate
203.0Moderate
213.0Moderate
223.0Moderate
233.1Moderate
243.1Moderate
253.1Moderate
263.2Moderate
273.2Moderate
283.2Moderate
293.3Moderate
303.3Moderate
313.3Moderate
Planning a trip in January

Hazard calendar for Boulder

In seasonPeak

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

Boulder's rainy season runs March–October, when most of the year's rain falls.

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

Is January a good time to visit Boulder?

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

0.0
Sightseeing
10th-best month of the year
0.0
Beach & pool
8th-best month of the year

January is a weaker month for outdoor sightseeing in Boulder.

What to pack for Boulder in January

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

In January, Boulder sees daytime highs around 37°F and nights near 14°F. Pack a warm layer and a heavy coat. About 6 days see rain.

a warm layera heavy coat

UV index in Boulder 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 Boulder peaks around July 13 at about 11 (extreme) — 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 highExtremeVery highHighModerateJul 13UV 11Dec 23UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar7High
Apr6High
May7Very high
Jun11Extreme
Jul11Extreme
Aug10Very high
Sep7Very high
Oct5High
Nov3Moderate
Dec2Low

Air quality in Boulder 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 Boulder 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).

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateAug 1620 µg/m³May 1113 µg/m³
PM2.5 (µg/m³)Level
Jan17Moderate
Feb15Moderate
Mar16Moderate
Apr13Moderate
May13Moderate
Jun14Moderate
Jul14Moderate
Aug21Moderate
Sep13Moderate
Oct15Moderate
Nov15Moderate
Dec16Moderate
Location & terrain

Where is Boulder?

Boulder sits at 40.0°N, 105.3°W, 5,328 ft above sea level, in United States. The nearest listed city is Louisville, 8.1 mi away.

Topography around Boulder

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

Within 2 miles, the terrain around Boulder has significant variations in elevation — a maximum elevation change of 1,703 ft around an average of 5,495 ft above sea level; within 10 miles, very significant variations in elevation — a maximum elevation change of 4,147 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 9,623 ft.

The land around Boulder is covered by trees (45%) and artificial surfaces (39%) within 2 miles, grassland (44%) and trees (41%) within 10 miles, and trees (41%) and grassland (34%) within 50 miles.

2 miles
1,703 ft
10 miles
4,147 ft
50 miles
9,623 ft
treesgrasslandcroplandartificial surfacesbare terrainwatermoss and lichen
January weather nearby: Louisville 8.1 mi · Lafayette 9.9 mi · Broomfield 12 mi · Erie 12 mi · Longmont 14 mi · Westminster 17 mi · Northglenn 17 mi · Arvada 17 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 Boulder (40.015°, -105.2706°, elevation 5,328 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).