Weather in Boston in January

The month to avoid. Of the twelve, January is the one to avoid. Highs sit at 0.8 °C and the day is short; this is an indoors-with-excursions month, not an outdoors-all-day one.

January ranks 12 of 12 — near the bottom of Boston's year. September is the month that works, and the swing between the two is 60 points, which is a different holiday rather than a slightly better one.

Rain on 9 days, 3 of them heavy. Enough to need a plan B, not enough to need a plan around it. Layers, and a genuinely waterproof outer — at 0.8 °C the difference between a good day and a miserable one is entirely down to what you are wearing.

What the averages hide

Averages flatten a month, and this one hides a few things: 28 nights drop below freezing, so anything left outside stays frozen. Across the twenty years measured, the hottest January day reached 18.3 °C and the coldest night fell to -23.9 °C, and the wettest single day dropped 45 mm — roughly 56% of the month's rain in one day.

January is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest January on record still delivered 138 mm against 28 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 80 mm average is a reasonable planning figure, not a promise.

Wind is light at 3.7 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 88%, which at 0.8 °C means damp rather than muggy — the kind of cold that gets into a coat and stays there.

How January sits in the year

This is a turning point in the year — December and February sit on opposite sides of it, so the month contains the change rather than following it.

Daylight in January

January sits at the dark end of Boston's year — 9.4 hours of daylight against 15.3 at midsummer, gaining 0.8 hours across the month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

Sea temperature

The sea sits at about 6.3 °C in January — too cold to swim without a wetsuit. The sea peaks at 19.7 °C in August and bottoms out at 4.6 °C — water lags the air by a month or two, which is why the best swimming often comes after the best weather.

How busy it gets

Off season. The genuine off season: cheapest by a distance, with the caveat that some tours and restaurants close entirely.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

January in Boston versus nearby

If Boston is one option among several, the nearby comparison is worth making. New York City is close enough to be a coin toss — 2.7 °C warmer, the same number of rain days. Bar Harbor is close enough to be a coin toss — within a degree on temperature, 1 day more rain.

So: January is a compromise. September is 60 points better and is what Boston is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Boston

See all twelve months in Boston, or where else to go in January.