Fall Frost?!

We got a good taste of the “feel of fall” this weekend, with below normal temperatures and a cool Saturday night!  Lows this morning dropped into the mid to upper 30s in NW Massachusetts and in and around Norwood, as expected – and I found myself grabbing for the extra blanket at about 3am last night (this morning).  These temps were the coolest they’ve been since the middle of May!  Did you like it?  Well, you’re in luck because we’re in for another night of clear skies, light wind, dry air… all of the ingredients necessary for radiational cooling.

Rob Eicher did a great job explaining radiational cooling in his blog today, and I wrote about it in my blog last night as well.  Really simply put, the clouds can sometimes act as a “blanket” for us and keep the heat from the day in closer to the surface.  On a night like tonight, with clear skies and little to no wind to keep our air “mixed,” that heat moves up and out – and the air temps drop quickly.  Tonight’s temps will be even cooler than last night – So, the area covered in a Frost Advisory issued by the National Weather Service has expanded from last night’s advisory.

It’s all a bit tricky as far as why some areas are covered in the advisory and others aren’t… and why, if temps aren’t expected to drop down to 32°F (the freezing point of water), how could we possibly see frost form (this is another thing that Rob did a great job explaining in his blog)?  The areas that are included in the advisory will likely see a widespread frost, and these areas are still considered to be in the growing season.  In fact, this “first frost” is a couple of weeks early, compared to the “average” first frost.  Basically, the idea of the advisory is to give you a heads up if you still plan on keeping your garden going for a little while longer.  It’s like saying “Hey, we don’t typically get frost this early in the season – but we probably will tonight, so here’s your heads-up to plan ahead.”  So, what should you do?  If you would like to keep the tomatoes, strawberries, lettuce, etc. alive – either bring the potted plants indoors, or “tuck them in before bed.”  What I mean by that is, throw an old blanket (or plastic) over the garden to “keep them warm” overnight.  You’re welcome to read the plants a good bedtime story while you’re at it.  It can’t hurt.

Now, how about the areas that are NOT under the advisory?  It’s not out of the question that a few spots NOT covered in the advisory could still see some patchy frost – but it’s not expected to be widespread.  So, the question is “should I cover my plants even though my house is not under that purply-blue color on your nifty little map up there?”  Last night when I was doing some Googling on the subject, I found this great gem of advice on a gardening website:  “It’s kind of like going to Las Vegas, but instead of gambling with your money, you put your tomato plants up on the blackjack table. (Editors Note: For your own safety, DO NOT attempt this in any gaming establishment.)”  Let me decode for you:  Don’t take the gamble if Mr. Tomato plant is still producing fruit.  Just tuck him in tonight anyway to play it safe.  The other thing is – for the rest of this week, all of the forecast lows are in the upper 40s to low 50s… which means, if you can bring your plants through tonight, they just may last for another couple/few weeks!  ***  Along the coastline, the Cape and of course the “urban heat island” of Boston will not have to worry about this.  Temps for these areas will be in the mid to upper 40s tonight.

After our very chilly Monday morning, we’re in for a really pleasant afternoon.  Temps will be in the mid to upper 60s again tomorrow under mostly sunny skies.  Clouds don’t start to sneak in until late in the day.  So, even though it’s Monday, try and enjoy this crisp fall feel!  Wet weather arrives on Tuesday, and the rest of the week looks unsettled (and the forecast is very uncertain…)  Stay tuned.  – Breezy