As the sun rose on the East Coast an arctic front was evident, passing into the Atlantic. The strong gradient between high and low pressure will propel dense, heavy, and very dry cold air into all of New England over the next 24 hours.
You can see on the graphic below as the arctic front arrived temperatures dropped nearly 10 degrees and will continue their tumble throughout the day. Winds shifting from southwest to northwest was another indicator of the passage of the front.
The peak of this chill will occur early Saturday morning. In Boston there’s no doubt the record low of minus 2 set back in 1896 is going to be shattered. Of interest is just how cold we will go. There is actually an outside chance that Logan Airport reaches 5 below zero by midnight, which would tie the record for today, set in 1881, but it’s a small chance.
Of the top 20 coldest mornings since 1872, only one has occurred this century, and if we see a double-digit subzero reading Saturday that would be the coldest since 1957. It’s likely Logan Airport ends up somewhere between minus 8 and minus 11.
The specific low on Saturday matters more for nature than us. Temperatures at or below minus 10 are cold enough to kill peach blossoms even though they are dormant. This would be the second time since 2016 this has happened and it impacts local farms. These temperatures are hard on birds and other wildlife, but they can hunker down out of the cold; a peach tree can’t move anywhere.
Of course we’ve all heard about the windchill that is going to accompany this arctic air. During the day Friday windchill readings will generally be from 5 to 15 below zero, but as we approach sunset they will drop to between 15 and 35 below.
Because the wind is not constant, neither is the windchill reading. At times when the winds subsides windchill readings rise, only to fall again during the strongest gusts. The numbers you hear and read about are often the extreme, not what is experienced consistently.
The chart above shows the most dangerous windchill readings between 7 p.m. Friday and 7 a.m. Saturday morning; thereafter temperatures will rise. Twenty below zero windchill readings are when we start to see frostbite occur in a short amount of time. If skin is covered, the windchill times are not relevant as they are calculated for bare skin.
Nevertheless, you can still eventually get frostbite even with gloves and hats — it takes much longer, however.
Another interesting aspect of this cold is how fast it departs. If Boston reaches 8 below zero Saturday morning and rises to 44 degrees Sunday afternoon it would be one of, if not the greatest, 30-hour increase in temperature ever recorded at the airport.
After the extreme cold of Friday and Saturday, I don’t see any more arctic air in sight and temperatures will be above average for much of the first half of February.