Freeze warning issued for parts of Massachusetts; Map shows how cold it will be Friday

A freeze warning has been issued for parts of Massachusetts as the weather forecast calls for temperatures to plummet in the Boston area late Thursday night into Friday morning.

It has been one of the warmest starts to October on record, but all of that is about to change. A crisp, chilly airmass is bringing the coldest air of the season thus far.

How cold will it be in Boston?

High temperatures on Thursday will be some 20-to-25 degrees colder than what we have been experiencing in recent days.

But it is Thursday night when the real chill arrives.

With clear skies, dry air and light winds, temperatures will drop like a rock Thursday night into early Friday. This has prompted the National Weather Service to issue a freeze warning from 11 p.m. Thursday to 9 a.m. Friday.

Most of the northern and western suburbs of Boston will bottom out between 28 and 32 degrees around 6-to-7 a.m. on Friday.

First frost

You can see that in a typical year, areas like northern Worcester County and the Berkshires have their first frost in late September.

Areas in green and yellow in the picture typically have their first frost/freeze right around now - right on schedule.

As a reminder, a frost occurs when the water vapor in the air freezes on contact with surfaces like grass and your windshield. This can actually occur in temperatures near or slightly above 32 degrees. A frost doesn't always lead to the death of vegetation.  

A freeze on the other hand is much more deadly to existing, tender plant life. A freeze occurs when temperatures are at or just below 32 degrees, this what we expect in those areas north and west of Boston early on Friday.

Therefore, we do expect significant damage to plants.

Protecting plants from freezing

Here's the thing about Friday morning's freeze, it is likely to be a "one-off" as we do not expect any similarly cold mornings for at least a week or more in the following days.  

So, if you want to keep your mums or other plants and flowers alive for a while longer, take some steps before you go to bed Thursday night.  

For potted plants, you can simply bring them indoors for the night.  

For vegetation in the soil, you have several options. You can cover them with a cloth or blanket, give them some extra water the night before or even load up the base with some additional mulch.  

Does it seem like the growing season is lasting a bit longer than it once did? This is true. Climate change has pushed our first frost and freeze dates nearly a week longer on average in the Boston area over the last 50 years.  

The fall season has been the second fastest warming season (only behind the winter) in our area over the last several decades.