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Chelmsford has a humid subtropical climate.
Hot, humid summers. Cool-to-cold winters. Rain in every month of the year — here's what that means in plain terms.
What this climate feels like
The four things a regular visitor actually wants to know:
Highs near 84°F in July. About 11 days a year above 90 °F.
Lows near 19°F in January. About 133 freezing nights a year.
About 50 in of rain a year, plus 64 in of snow. Snow falls through the winter months.
A roughly even mix of sun and cloud.
What "humid subtropical" means
Climate scientists sort every place on Earth into about 30 climate types, based on how hot, cold, wet and dry it is across the year. Chelmsford's type — humid subtropical — sits in the broad family of mild, temperate climates. Despite the name, it does not mean tropical or frost-free: Chelmsford still has cool-to-cold winters.
Researchers write climate types as a short letter code. Here is what each letter means:
Cities with the same climate as Chelmsford
A humid subtropical climate (Cfa) — these recognizable cities share it. If you know one of them, you know roughly what to expect.
Chelmsford sits near a climate boundary
This city sits right on the line between humid subtropical and the next type along. Different climate maps file it on different sides of that line; the lived weather doesn't change at the line — it's a naming boundary, not a wall.
Has Chelmsford's climate type changed?
A climate type is a coarse bucket. It can hold steady for years while the weather inside it shifts — or tip into the next bucket.
What this climate means for you
Warm-season grasses and broad-leaved evergreens thrive; gardens are productive but humidity brings fungal pressure. Frost is occasional, so tender perennials often overwinter.
Spring and autumn are pleasant; summer is hot and humid; winter is mild and a fine alternative to escaping cold further north.
Hot, sticky summers and mild winters — air conditioning runs hard from late spring to early autumn. Storm season needs preparation in coastal areas.
Where these numbers come from
The climate type and the month-by-month figures on this page are computed from Chelmsford's measured 30-year climate normals (1991–2020) — the same official records behind Chelmsford's main climate page, so the two always agree.
Long-range climate maps measure things slightly differently and can place a city in a neighbouring category. Where they differ, this page uses the measured station record as the climate today.
Methodology & sources
Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Reading (NOAA GHCN station USC00196783), about 22 km from the city centre.