Spotty, Light Rain Early Then Dry Monday – CBS Boston

BOSTON (CBS) – For the first time in its 124 year history, the Boston Marathon is not being run in April. by 1968, the Marathon was run on April 19th, Patriot’s Day. It was then moved to the third Monday in April and has stayed there ever since. From a meteorologist’s perspective, this is just about ideal. October in Boston comes with much fewer possible weather complications than does April. I don’t have to tell any native New Englander that April can be quite fickle here.

Just take a peek at Boston Marathon history:

87 degrees on April 16, 2012
28 degrees on April 19, 1926

How about the last two Boston’s? We had a record 1.57 inches of rain in 2018 and 0.72″ of rain in 2019 along with some nasty thunder and lightning.

(WBZ-TV graphic)

Then there’s the sea breeze in April, the water temperatures are frigid, in the 40s. So, any kind of day with comparatively light wind and decent heating of the land and you could have a 20-to-30 degree difference along the route from Hopkinton to Boston. Runners can literally experience two thoroughly different seasons along the 26 mile route.

(WBZ-TV graphic)

In October, sea breezes are basically non-existent with much warmer ocean temperatures. The land-based temperature extremes on either end are also less emotional. for example, look at the records for October 11:

Record high: 82
Record low: 32

These are about 5-to-10 degrees less extreme than the typical marathon dates in April.

Essentially, in October, there really is very little concern of a harsh weather day with one exception, tropical systems. We are just past the peak of our hurricane season in October and typically there is always something to watch in the Atlantic or Caribbean this time of year. Of course, the chances of a hit in Boston on any given day is very low.

And that brings us to our first October Boston Marathon here in 2021.

As we have been tracking the forecast over the last few weeks, it was fairly clear that the likelihood of an “extreme” weather day was low. Conditions have been overall mild, but not anywhere near record territory. We haven’t had a frost anywhere close to Boston however, heck we haven’t already dropped below 50 however in Boston (and that is nearing a record for latest ever). The Tropics have also calmed in recent weeks, currently there are no named systems anywhere in the Atlantic basin.

Thinking back on the summer and fall here in 2021, if I were to ask you what you would guess would be our biggest weather threat on Marathon Monday I bet almost all of you would guess one thing – rain. And you would be correct! Boston is currently more than a foot of water above the average to date this year and we just came out of the wettest July-August-September stretch ever recorded, so naturally there would be some rain in the forecast.

But alas, I come with good news! The latest indications are that any rain we might receive Sunday and Monday would be very light, spotty and also moving out before the Marathon.

Let’s break down the details:

A ridge of high pressure begins to lose its grip on the vicinity, as an area of low pressure well to the south slowly moves northward. Rain chances will increase on Sunday, but most of the heavy rain stays offshore. Expect mainly cloudy conditions with temperatures in the 60s.

The morning should be dry, but a few showers may develop by midday and into the afternoon. Highest risk will be across southern parts of the state, but already in the Boston area, a shower or two can’t be ruled out. The chance of a shower is possible by early Monday before this offshore system pulls away and takes the rain with it.

So for Monday itself, while Hopkinton may be stuck in the clouds to start with some early morning fog, Boylston Street might have a break of sun by the end of the race. already with the slight chance of showers early on, most of the day should stay dry. Temperatures will mostly be in the 60s.

(WBZ-TV Graphic)

Hour-by-hour forecast Monday:

6 a.m: Hopkinton 55, Boston 60, mainly cloudy, wind NE 4-8mph
9 a.m: Hopkinton 60, Boston 65, mainly cloudy, wind ENE 5-10mph
Noon: Temperatures 68-72, breaks of sun, wind E 5-10mph
3 p.m: Temperatures low to mid 70s, breaks of sun, wind E 5-10mph
6 p.m: Temperatures 65-69, Pt. Sunny, wind E 4-8mph

Probably a bit warmer than most runners would like, but looks like a terrific day for spectators!

If you are one of the thousands of runners this year, on behalf of the complete WBZ-TV Weather Team I wish you good luck and great weather!

As always, I would urge that you stay tuned to updated forecasts this weekend on WBZ-TV, and CBSN Boston.

Follow Terry on Twitter @TerryWBZ

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