Chelmsford weather in January

In January, Chelmsford sees average daytime highs of 35°F and overnight lows near 21°F, with 3.3 in of precipitation across 9.6 wet days and about 9.2 hours of daylight. It is the 12th-warmest and 9th-wettest month of the year here.

Day-to-day highs hold fairly steady near 35°F through the month. The sky is clear or mostly clear about 35% of the time in January, and the air most often feels dry.

Daylight stretches from about 8 h 54 min at the start of January to 9 h 42 min by month's end. Set against the rest of the year, January is Chelmsford's 4th-clearest and 2nd-windiest month. For the whole year in context, see Chelmsford's year-round climate.

Daytime high
35°
12th warmest
Overnight low
21°
1st coldest
Precipitation
3.3 in
9.6 wet days
Daylight
9 h 12 min
7:19 AM – 4:31 PM
Cloud cover
57%
4th clearest
Wind
8 mph
2nd windiest
Solar energy
1.98 kWh/m²
Travel score
0.0
out of 10

Chelmsford is town in Middlesex County, Massachusetts, United States.

Founded
1633

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 35°F through the month.

A typical January day in Chelmsford reaches about 35°F in the afternoon and slips back to 21°F overnight — a 14°F spread between the day's warmth and the night's chill. On most days the high lands between 22°F and 49°F. Set against its neighbours, January runs about 5°F cooler than December and about 2°F cooler than February.

20°40°151015202531
Avg high (°F)Avg low (°F)
13723
23723
33723
43723
53623
63622
73622
83622
93622
103622
113521
123521
133521
143521
153521
163520
173520
183520
193420
203420
213420
223420
233420
243420
253520
263520
273520
283520
293520
303520
313520

How January really feels in Chelmsford

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
30 feel bitter (≤ 14°F)

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

Chelmsford weather by month

How January compares with the rest of the year at a glance. January is the 12th-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan35° / 21°3.39.66.29.20.0
Feb38° / 22°3.08.65.710.30.0
Mar45° / 30°4.2114.911.61.0
Apr57° / 40°3.710.61.213.13.9
May67° / 49°3.110.5014.46.0
Jun76° / 59°3.410.7015.16.5
Jul82° / 65°3.110.3014.86.1
Aug80° / 63°3.49.5013.76.6
Sep73° / 56°3.38.3012.37.0
Oct62° / 45°3.89.50.210.85.3
Nov50° / 35°3.49.31.19.62.3
Dec40° / 27°4.210.34.78.90.2

Cloud cover in January

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 35% of the time in January.

Beyond those clear spells, partly cloudy skies cover about 16% of January, with mostly cloudy or overcast conditions the remaining 49%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15149
25149
35050
45050
55050
65050
75050
84951
94951
104951
114951
124951
135050
145050
155050
165050
175050
185149
195149
205149
215149
225149
235248
245248
255248
265248
275248
285248
295248
305248
315248

Chance of precipitation in January

Any precipitationSnow

Chelmsford gets around 3.3 in of rain and snow over 9.6 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 31% and peaks near 33% on the wettest days, and about 6 days bring snow.

0%10%20%30%40%151015202531
Rain chance (%)Snow chance (%)
13218
23318
33319
43319
53320
63320
73320
83321
93321
103321
113322
123322
133322
143322
153222
163222
173221
183121
193121
203021
213020
222920
232920
242919
252819
262819
272819
282818
292818
302818
312818

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 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 8 h 54 min at the start of January to 9 h 42 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 48 minutes over January. Sunrise moves from 7:21 AM to 7:09 AM, and sunset from 4:16 PM to 4:49 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
18.97:214:16
28.97:214:17
38.97:214:18
49.07:214:19
59.07:214:20
69.07:214:21
79.07:214:21
89.07:214:22
99.07:214:23
109.17:214:24
119.17:204:25
129.17:204:26
139.17:204:27
149.17:204:29
159.27:194:30
169.27:194:31
179.27:184:32
189.37:184:33
199.37:174:34
209.37:174:35
219.37:164:36
229.47:164:38
239.47:154:39
249.47:144:40
259.57:144:41
269.57:134:43
279.57:124:44
289.67:114:45
299.67:114:46
309.67:104:48
319.77:094:49

Solar energy in January

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in January, about 1.98 kWh/m².

For context, solar energy here swings from a low near 1.59 kWh/m² to a high of 5.9 kWh/m² in July across the year — January's 1.98 kWh/m² sits near the bottom.

0123151015202531
Solar energy (kWh/m²)Level
11.7Dim
21.7Dim
31.7Dim
41.7Dim
51.7Dim
61.7Dim
71.8Dim
81.8Dim
91.8Dim
101.8Dim
111.8Dim
121.8Dim
131.9Dim
141.9Dim
151.9Dim
161.9Dim
172.0Dim
182.0Moderate
192.0Moderate
202.1Moderate
212.1Moderate
222.1Moderate
232.2Moderate
242.2Moderate
252.2Moderate
262.3Moderate
272.3Moderate
282.3Moderate
292.4Moderate
302.4Moderate
312.4Moderate
Planning a trip in January

Hazard calendar for Chelmsford

In seasonPeak

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

Chelmsford 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 Chelmsford?

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

0.0
Sightseeing
11th-best month of the year
0.0
Beach & pool
9th-best month of the year

January is a weaker month for outdoor sightseeing in Chelmsford.

What to pack for Chelmsford in January

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

In January, Chelmsford sees daytime highs around 35°F and nights near 21°F. Pack a warm layer and a heavy coat. Worth having: rain gear. About 10 days see rain.

a warm layera heavy coatrain gear

Sea temperature near Chelmsford in January

The nearest coast averages about 41°F in January — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 29 mi away) is warmest in August at about 66°F and coldest in February near 38°F.

The water stays below 68°F all year — cool enough that most swimmers want a wetsuit.

40°50°60°70°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshing
Sea temperature (°F)Comfort
Jan41Bracing
Feb38Bracing
Mar38Bracing
Apr42Bracing
May50Bracing
Jun58Bracing
Jul65Cool
Aug66Cool
Sep63Cool
Oct56Bracing
Nov50Bracing
Dec46Bracing

UV index in Chelmsford in January

LowModerateHighVery highExtreme

Clear-sky midday UV in January peaks around 1. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Chelmsford peaks around July 10 at about 7 (very high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near January 1 at about 1 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighHighModerateLowJul 10UV 7Jan 1UV 1
UV index (midday)Level
Jan1Low
Feb3Moderate
Mar4Moderate
Apr5High
May7Very high
Jun7Very high
Jul7Very high
Aug5Moderate
Sep6High
Oct3Moderate
Nov2Moderate
Dec1Low

Air quality in Chelmsford 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 Chelmsford is worst in July — around 16 µg/m³ PM2.5 (moderate), about 2.0× the cleanest month (November, 8 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1715 µg/m³Nov 188 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb13Moderate
Mar13Moderate
Apr13Moderate
May14Moderate
Jun13Moderate
Jul16Moderate
Aug14Moderate
Sep11Good
Oct9Good
Nov8Good
Dec9Good
Location & terrain

Where is Chelmsford?

Chelmsford sits at 42.6°N, 71.4°W, 246 ft above sea level, in United States. The nearest listed city is Lowell, 3.7 mi away.

Topography around Chelmsford

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

Within 2 miles, the terrain around Chelmsford has only modest variations in elevation — a maximum elevation change of 318 ft around an average of 210 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 515 ft; within 50 miles, large variations in elevation — a maximum elevation change of 3,176 ft.

The land around Chelmsford is covered by trees (79%) within 2 miles, trees (80%) within 10 miles, and trees (75%) within 50 miles.

2 miles
318 ft
10 miles
515 ft
50 miles
3,176 ft
treesgrasslandcroplandartificial surfaceswaterwetland
January weather nearby: Lowell 3.7 mi · Westford 3.7 mi · Billerica 5.6 mi · Dracut 5.6 mi · Tewksbury 6.8 mi · Acton 8.7 mi · Concord 9.9 mi · Wilmington 11 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 Chelmsford (42.5998°, -71.3673°, elevation 246 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). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. 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).