Best chance of frost will be west of 495 this weekend

By Terry Eliasen, Meteorologist, WBZ-TV Exec. Weather Producer

BOSTON - There is a chance of some scattered frost early Sunday morning. Best chance would be well north and west of Boston.

We should see lots of lows in the mid to upper 30s near and outside of 495.

This should be just cold enough for the first frost to appear on the grass in some of the colder, far northwestern 'burbs.  Not expecting a killing freeze yet.

Frost is always a possibility this time of year when temperatures drop into the 30s and you have light winds. Even though the temperature on your thermometer (well off the ground) may read mid 30s, cold air sinks to the very ground level and with just a small amount of moisture in the air, it can freeze and adhere to surfaces. 

The winds are key. . . even a small amount of wind works to keep the air "mixed" and does not allow the ground to cool off as much. The best chance for frost occurs when there is little to no wind and maximum radiation of heat can take place.

Here are the average first frost times for our area:

As you can see on this chart (for Keene, NH), Sunday morning is really the only morning there are frost concerns

In summary, it does not appear as though you will need to bring in or protect your plants Saturday night inside of 495 or in eastern Mass. However, if you live in a typically colder location, west of 495, you may want to consider taking some action. Good news is that even in the coldest of areas, we are not expecting anything near a freeze or killing freeze, just a bit of an early morning frost.