Chatham, Massachusetts climate: Normal weather by month, frost dates and records
Chatham's normal year runs from 26°F January nights to 79°F July afternoons, with 45.2 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 10.5°C, January lows of −4°C, July highs of 26°C, 1,148 mm of precipitation a year.
- NOAA stationChatham Municipal Airport
- Station IDUSW00094624
- Location41.69°N 69.99°W
- Elevation68 ft (21 m)
- From the center2 miles
- Population (town)6,711
- Census place1,614
On October 23, the normal high in Chatham is 59°F and the normal low 45°F, and the chance of measurable rain or snow is 44%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Chatham.
- Jan 39° 26°
- Feb 40° 26°
- Mar 44° 31°
- Apr 52° 39°
- May 62° 48°
- Jun 72° 57°
- Jul 79° 64°
- Aug 78° 64°
- Sep 71° 58°
- Oct 61° 47°
- Nov 52° 39°
- Dec 44° 31°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Chatham each month?
July is the warmest month, with normal highs of 79°F; January the coldest, with normal lows of 26°F. The most precipitation falls in December (5.00 in), the least in July (2.79 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 39°F | 26°F | 32.1°F | 3.75 | 14 | <1 | 23 | 9 h 30 min |
| February | 40°F | 26°F | 32.7°F | 3.61 | 13 | <1 | 22 | 10 h 30 min |
| March | 44°F | 31°F | 37.6°F | 4.43 | 13 | <1 | 17 | 11 h 50 min |
| April | 52°F | 39°F | 45.6°F | 4.01 | 14 | <1 | 4 | 13 h 20 min |
| May | 62°F | 48°F | 55.0°F | 3.34 | 13 | <1 | <1 | 14 h 30 min |
| June | 72°F | 57°F | 64.3°F | 2.95 | 13 | <1 | <1 | 15 h 10 min |
| July | 79°F | 64°F | 71.4°F | 2.79 | 11 | 1 | <1 | 15 h |
| August | 78°F | 64°F | 70.6°F | 3.03 | 11 | <1 | <1 | 13 h 50 min |
| September | 71°F | 58°F | 64.3°F | 3.58 | 13 | <1 | <1 | 12 h 30 min |
| October | 61°F | 47°F | 54.3°F | 4.23 | 14 | <1 | 1 | 11 h 10 min |
| November | 52°F | 39°F | 45.4°F | 4.47 | 13 | <1 | 8 | 9 h 50 min |
| December | 44°F | 31°F | 37.3°F | 5.00 | 14 | <1 | 19 | 9 h 10 min |
| Year (annual) | 58°F | 44°F | 50.9°F | 45.19 | 155 | 1 | 92 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 4°C | −4°C | 0.1°C | 95 mm |
| February | 4°C | −3°C | 0.4°C | 92 mm |
| March | 7°C | 0°C | 3.1°C | 113 mm |
| April | 11°C | 4°C | 7.6°C | 102 mm |
| May | 17°C | 9°C | 12.8°C | 85 mm |
| June | 22°C | 14°C | 17.9°C | 75 mm |
| July | 26°C | 18°C | 21.9°C | 71 mm |
| August | 25°C | 18°C | 21.4°C | 77 mm |
| September | 22°C | 14°C | 17.9°C | 91 mm |
| October | 16°C | 9°C | 12.4°C | 107 mm |
| November | 11°C | 4°C | 7.4°C | 114 mm |
| December | 7°C | −1°C | 2.9°C | 127 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. Chatham's own co-op station Chatham station does: 25 inches of snow in a normal year (see the other stations below).
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094624; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Chatham?
Normal highs sit between 65°F and 85°F in June, July, August and September. Of those, July has the fewest days with rain (11).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094624.
When is the last frost in Chatham?
In Chatham, the last spring frost (32°F) comes after April 13 in half of years and after April 26 in one year in ten; the first autumn frost comes before November 4 in half of years and before October 21 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 131 year in 10 after April 26; 9 in 10 after April 1
- First autumn frost, half of years before
- November 41 year in 10 before October 21; 9 in 10 before November 18
NOAA puts the median frost-free season at 206 days, and the season without a hard freeze (28°F) at 234 days.
A hard freeze (28°F) comes after March 31 in half of springs and before November 19 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Chatham in zone 7b in ZIP code 02633. By the map's own method, the average of each year's coldest night over 1991-2020, Chatham's NOAA station is in zone 7b: the coldest night of a typical year reaches 7°F (23 complete years).
Frost dates for every NOAA station in Massachusetts · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00094624; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Chatham?
In a normal year in Chatham, 1 day a year reaches 90°F, 92 nights fall to 32°F or colder and 155 days bring measurable precipitation.
- Days at 90°F or more
- 1a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 92a normal year
- Days that stay below freezing
- 16high of 32°F or less
- Days with 0.01 inch of precipitation
- 155a normal year
The highest temperature in this station's record (since 1996) is 99°F, on July 5, 1999; the lowest is −5°F, on January 16, 2004.
The wettest calendar year on that record is 2019, with 54.02 in.
Source: NOAA NCEI 1991-2020 annual normals, station USW00094624; records: ACIS (NOAA Regional Climate Centers), station USW00094624. Records use complete months only; a month missing more than three days is left out.
How sunny is Chatham?
Over a year 72% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Chatham, 3.9 kWh per square metre a day. August is the sunniest month (79%) and December the cloudiest (59%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 60% | 1.6 |
| February | 66% | 2.5 |
| March | 67% | 3.7 |
| April | 71% | 4.9 |
| May | 71% | 5.5 |
| June | 74% | 5.9 |
| July | 78% | 6.0 |
| August | 79% | 5.4 |
| September | 79% | 4.4 |
| October | 72% | 3.0 |
| November | 66% | 1.9 |
| December | 59% | 1.4 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Chatham need?
A normal year in Chatham brings 5,622 heating degree days, 5% more than the median U.S. place (5,373), and 512 cooling degree days, 44% fewer than the median (908). Eight months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 2,567 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,021 | 0 |
| February | 904 | 0 |
| March | 851 | 0 |
| April | 581 | 0 |
| May | 314 | 3 |
| June | 80 | 61 |
| July | 6 | 205 |
| August | 7 | 181 |
| September | 79 | 58 |
| October | 335 | 4 |
| November | 587 | 0 |
| December | 857 | 0 |
| Year (annual) | 5,622 | 512 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00094624. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Chatham been warmer than normal lately?
2025 averaged 51.1°F, 0.2°F above the 1991-2020 normal of 50.9°F. 4 of the 4 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 52.9°F | +2.0°F | 43.32 |
| 2022 | 53.8°F | +2.9°F | 41.11 |
| 2023 | 55.3°F | +4.4°F | – |
| 2025 | 51.1°F | +0.2°F | – |
Source: observed years: ACIS, station USW00094624. A year counts only with all twelve months complete.
How does Chatham's climate compare?
Chatham is warmer than 28 of the other 34 places with their own NOAA record in Massachusetts, and wetter than 11. Across the 7,247 U.S. stations with normals, its annual mean of 50.9°F is warmer than 44%.
In the Köppen classification computed from these normals, Chatham is Cfb: temperate, no dry season, warm summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Chatham share this climate record?
6 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- East Harwich, MA5,670 people · 2 mi NW
- Provincetown, MA3,729 people · 27 mi N
- North Eastham, MA1,958 people · 10 mi N
- Brewster, MA10,447 people · 6 mi NW
- Orleans, MA6,485 people · 7 mi N
- West Chatham, MA1,337 people · 0 mi S
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
What do Chatham's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Chatham. This page uses Chatham Municipal Airport; the other differs by site and elevation:
| Station | From the center | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Chatham station USC00191386 | 1 mi S | 40 ft | 50.3°F | 25°F | 76°F | 45.9 | 25 | April 5 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Chatham's climate
What is the coldest month in Chatham?
January, with a normal high of 39°F and a normal low of 26°F. The warmest is July (79°F by day, 64°F at night).
Does it snow in Chatham?
Yes. NOAA publishes no 1991-2020 snowfall normal for Chatham's NOAA station; Chatham's own co-op station Chatham station records 25 inches of snow in a normal year.
What is the rainiest month in Chatham?
December, with 5.00 in of precipitation in a normal year; the driest is July with 2.79 in.
What plant hardiness zone is Chatham in?
The USDA's 2023 map puts Chatham in zone 7b in ZIP code 02633. By the same method at Chatham's NOAA station, the coldest night of a typical year reaches 7°F (23 years, 1991-2020): zone 7b.
How late can frost come in Chatham?
In half of years the last 32°F night comes after April 13; in one year in ten it comes after April 26. Waiting until April 26 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Massachusetts climateThe statewide normals and every place in the state
- West Harwich, MA7 miles from this station, 50.4°F a year
- Hyannis Barnstable Municipal Airport, MA15 miles from this station, 51.5°F a year
- Barnstable, MA16 miles from this station, 50.3°F a year
- East Sandwich, MA25 miles from this station, 49.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made