A hard freeze is becoming increasingly more likely for Friday night as the forecast comes into a clearer picture.
Wednesday morning I narrowed down forecast temperatures bottoming out between 27-31 degrees Friday, Saturday, and Sunday nights. These temperatures are for the immediate Champlain Valley too, which typically is a warmer spot compared to other areas.
Temperatures could very well drop into the 20s and even some upper teens in some of the 'worst case scenarios' for the outdoor vegetation.
Cool temperatures are locked in across the northeastern United States and another reinforcing shot of cold air from Canada will come down Friday. A cold front will swing through early Friday morning and upper-level temperatures (about 5,000 feet above ground level) are forecast to drop to around 14-20 degrees. It unusually doesn't translate into 14-20 degrees at ground level, but 20s is a very safe bet in those conditions.
This week the National Weather Service started its annual freeze/frost campaign, where they will issue warnings/watches based on temperatures falling below certain levels in certain areas. This image (and the ones below) is courtesy Pete Banacos at the NWS Burlington office, a meteorologist who composed the average 'last freeze dates' in our area. You're looking at average dates of the last 32° reading we see in certain areas. The red line is the 'average' or the 'mean' date, while the box and whisker parts show 1/4 and 3/4 percentiles and then the extreme cases. The last 32° temperature reading in our area varies widely, because of our complex terrain. Typically the last freeze happens in mid May, with a range from late April to early June depending on the town.
Here are other last freeze dates (on average).
Now the important thing to note is, if you don't have a freeze warning or frost advisory over your county or town, it doesn't meant you're in the clear. These warnings/advisories are based on when the growing season begins. So if the Champlain Valley sees an advisory or warning in the coming days, that's because the growing season has started, but in other areas it hasn't. It may even get colder in other areas that aren't under the warning! So when you see one, note it's usually a region-wide cold. The NWS even made note of that in their Area Forecast Discussion Wednesday morning:
"IF ENOUGH CLRG SKIES...MOST CLDS NRN VT...LOOKING AT TEENS/20S ACRS
GOOD PORTION OF FA WHICH IS NOT GOOD CONSIDERING THE ADVANCED STAGE
OF PERENNIAL FRUIT TREES, ETC.
THE FROST/FREEZE PROGRAM BEGINS TODAY FOR CHMPL AND ST LWRNC VLYS
BUT STILL CLIMATOLOGICALLY TOO EARLY FOR REST OF FA. THUS THE
POTENTIAL OF FROST/FREEZE HEADLINES FOR CHMPL VLY/ST LWRNC VLY YET
NO HEADLINES FOR COLDER AREAS. I/VE SAID IT ONCE..I/VE SAID IT A
HUNDRED TIMES...IGNORE THE HEADLINES AND WATCH THE TEMPERATURES AND
IF THEY/RE EXPECTED TO BE SUB-FRZG THEN TAKE ACTION!!!"
On Friday and through the weekend it'll be a good idea to take any plants inside or protect them somehow. I know owners of orchards and vineyards will be watching the temperatures very closely and try to protect their product appropriately. We'll let you know if anything changes!