Boston Marathon

Here’s David Epstein’s weather forecast for the 2021 Boston Marathon

Does the Marathon Monday forecast include rain, extreme temperatures, wind, or humidity? Meteorologist David Epstein weighs in.

boston marathon starting line
The Boston Marathon starting line was painted on Main Street in Hopkinton. Lane Turner / The Boston Globe

The weather forecast is always important for the Boston Marathon, and the time of year makes this race unique.

In April, race day temperatures can be cold or hot. But in October, there’s a little bit less of a range of possibility for big heat or big cold — and that’s the case this year.

Here’s my complete forecast for the 2021 Boston Marathon:

How warm will it be during the marathon?

The sun is much lower in the sky this time of year than it would be in April. — TimeandDate.com

At sunrise Monday, temperatures will be just under 60 degrees in Hopkinton, rising toward — and even exceeding — that mark fairly quickly. By 2 p.m., it should be near 70 degrees with a slight bit of mugginess in the air.

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Temperatures will be in the mid-to-upper 60s for much of the race.

I’m expecting a lot of cloud cover, but the sun may poke through at times, especially as we get deeper into the morning and afternoon. Interestingly, this time of the year the sun is 20 degrees lower than in April. This factor will dramatically decrease the likelihood of getting a sunburn, which can often happen in the spring.

Will it rain on Marathon Monday?

Low pressure will pass south of New England on Sunday night and early Monday, and the rain shield could move far enough north to bring a quick early morning shower. This is just a small possibility, and if it does occur, the risk is gone by mid-morning.

And what about wind?

Wind will not be a big factor during the race. Any headwind will be slight.

The mild weather will continue into much of next week. Whether you’re visiting Boston, or this is your home, enjoy the race.

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