How extreme does Acton's weather get?

The hottest, coldest, wettest and snowiest days Acton has recorded — the outer limits of what its weather can do, and how far they sit beyond a normal day.

Based on 48 years of daily weather observations (1978–present), from the Lowell station 18 km away. Updated through May 2026 — an all-time extreme only changes when a more extreme day actually occurs, so some dates are old. That is normal, not stale data.

The four kinds of extreme

The hottest, coldest, wettest and snowiest single days Acton has recorded — each shown against what a normal day that time of year looks like.

🔥 Hottest day

103°F Jun 25, 2025

That is about 24°F hotter than a normal June afternoon in Acton (typical high near 79°F).

The three most extreme on record

1 103°F Jun 25, 2025recent

2 102°F Jun 11, 2008

3 102°F Jul 23, 2011

❄️ Coldest night

-17°F Jan 27, 1994

About 33°F colder than a normal January night in Acton (typical low near 16°F).

The three most extreme on record

1 -17°F Jan 27, 1994

2 -15°F Jan 28, 1994

3 -15°F Feb 15, 2015

🌧️ Most rain in one day

5.48 in Aug 20, 1991

More rain in a single day than Acton usually gets in the whole month of August (typical August total about 4.0 in).

The three most extreme on record

1 5.48 in Aug 20, 1991

2 5.11 in Oct 21, 1996

3 4.46 in Sep 11, 1999

⛄ Most snow in one day

22.1 in Feb 9, 2013

The three most extreme on record

1 22.1 in Feb 9, 2013

2 20.6 in Mar 14, 2018

3 18.8 in Mar 6, 2001

How hot and cold it gets, month by month

The shaded band is the normal range of daily temperatures for each month. The dots show the most extreme it has ever been — so you can see how far beyond a normal day the records really sit.

normal range of daily temperatureshottest ever recordedcoldest ever recorded

Acton's record heat sits well above even a hot day for the season — June's 103°F is about 24°F beyond a normal hot afternoon. Its record cold is just as far below a normal winter night — the dots mark how rare each extreme really is.

In plain terms

In a normal year, Acton's warmest days reach the mid-80s°F and its coldest nights drop to the mid-10s°F. But across the record it has gone as high as 103°F and as low as −17°F. A single day has delivered over 5 inches of rain or close to 22 inches of snow. Those are the outer edges worth knowing if you are moving here, planning a trip, or thinking about a house.

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 26 km from the city centre.

How we build these numbers →

← Acton city detail