What to know about this weekend’s frost and freeze advisories
Many areas will see their first frost or freeze of the season. But while Boston's low temperatures will be cold, they should remain warm enough to avoid frost.
Mid-October is often when the first frost occurs across many parts of southern New England. In Boston, frost frequently doesn’t develop until November. A first frost or freeze marks the end of the growing season, although some plants, like mums, will not succumb to cold weather until temperatures fall into the lower 20s or even teens, and that is still weeks away.
All of that said: The National Weather Service has issued a freeze advisory for the area roughly between Route 495 and Route 128 and a frost advisory for areas east of Route 128/95—including Boston—for tomorrow morning. (See the map below for more specifics.) These are areas that haven’t seen these conditions yet. Whether all areas of the city actually see frosty conditions on Saturday morning is still questionable.
Freeze and frost warnings are out for Saturday morning.
The reason you don’t see frost advisories west of Route 495 included in the above advisory is because those areas have already seen temperatures below freezing. The weather service won’t issue advisories once the condition occurs.
The chart below shows when frost typically occurs across Massachusetts. For Logan Airport, there’s less than a 10 percent chance of a 32-degree morning occurring this time of year. Typically, the first 32-degree day doesn’t take place until November! Although the frost advisory includes the coastline, I don’t believe most coastal communities will reach levels cold enough for a frost on Friday night and early Saturday. I suspect the official low temperatures at Logan Airport won’t even drop under 40 degrees.
Typical dates of first and last frost.
The last time Boston had a frost was April 10, 2016. That was about average for when the final freeze in spring occurs.
If you haven’t lost your plants in these areas, take them inside or cover them. You can do the latter with a row cover, a manufactured product made for frost protection or, simply, an old cotton sheet. Don’t use something like a tarp, as the plastic doesn’t breathe and you can do more damage than good to your plants.
This isn’t the beginning of a permanent cold wave. In fact, it’s typical in October for a night or two of cold to be followed by a period of mild weather. If you can get your plants to survive tonight, there’s a good chance they will continue to live not only for a few more days, but possibly for another week or two.
The cold mornings will continue to spread the color wave south and east this weekend. I expect fantastic colors in many places north and west of Boston, with the immediate metro area seeing peak color in another week to 10 days.
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