Weather in Boston in August

A good month. August works. It is not the peak, but nothing about it fights you. Highs average 28 °C, lows 17.2 °C, and rain falls on 11 days — nothing in the month is working against you.

August ranks 4 of 12 in Boston: past the worst of the year but short of September, which is the month to book if the dates are open.

Rain on 11 days, 3 of them heavy. Enough to need a plan B, not enough to need a plan around it. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

Averages flatten a month, and this one hides a few things: 9 days top 30 °C — hot spells arrive, but they break. Across the twenty years measured, the hottest August day reached 38.4 °C and the coldest night fell to 10.6 °C, and the wettest single day dropped 54 mm — roughly 58% of the month's rain in one day.

August is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest August on record still delivered 211 mm against 36 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 93 mm average is a reasonable planning figure, not a promise.

Wind is light at 1.4 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 73%.

How August sits in the year

Temperatures hold steady either side: 28 °C in July, 28 here, 24.3 in September. Nothing about the timing within the month matters much.

Daylight in August

14 hours of daylight, losing 1.2 hours across the month. That is between Boston's extremes of 15.3 and 9.1 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 19.7 °C in August — swimmable, but it takes a moment to commit. This is the warmest the water gets all year.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead.

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

August 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 — within a degree on temperature, 2 days more rain. Bar Harbor is close enough to be a coin toss — 5.6 °C cooler, 1 day more rain.

So: August works, with September the better month by 7 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Boston

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