Autumn is a transitional season when the heat of summer fades away and the chill of winter gradually returns. But, sometimes winter can be aggressive and show up overnight.
When this type of rapid temperature change happens, it is often called a Blue Norther. This is a fast-moving cold front marked by a quick and dramatic drop in temperature. A fall of 20 to 30 degrees in just a few minutes is not uncommon. They also usher in a dark blue sky and strong northerly winds. Hence, the name.
Blue Northers are most common in the central US, where there are few natural barriers to slow or block arctic air masses from moving south. They can occur throughout the year, but are most common between November and March.
One of the most famous examples of this weather phenomenon was the “Great Blue Norther” of November 11, 1911. As the front passed through the southern plains, temperatures dropped from highs in the 70s and 80s to the teens in just ten hours. In Oklahoma City, for example, the temperature reached a record high of 83°F in the afternoon and then plummeted to a record low of 17°F by midnight. Both records, according to the NWS, are still in place.
Twenty-four temperature changes from The Great Blue Norther of 1911. Credit: FOX
After a warm start to autumn, Mother Nature brought New York City a winter preview on Friday.
According to the NWS, the temperature in Central Park dropped to 29°F late Friday night. That was the coldest air the city has seen since March and marks the first freeze of the season.
Compared to the above-average temperatures the city has been experiencing this season, this first nip of frosty air was a bit jarring for some people. But, mid-November is when the city usually sees its first freeze. The earliest 32°F reading on record came on October 19 twice, first in 1940 and then again in 1974. Our latest first freeze was on December 22, 1998.
Produced by a deep dip in the jet stream, these chilly conditions are expected to last for a day or two. Then, after a brief warm-up, another shot of arctic air is forecast to hit the city next week. Keep those coats and gloves handy!
Average Dates for First Frost. Credit: Cornell
October was unusually warm in New York City this year. We had 19 out of 31 days post above-average readings with one day reaching a record-breaking 93°F. This unseasonable heat helped drive the city’s mean temperature for the month up to 59.9°F, which is 3°F above normal.
On the precipitation side of things, October was rather soggy. Overall, 15 days produced measurable rainfall that added up to 6.15 inches in Central Park. Of this total, more than half fell during just two storms. On average, the Big Apple gets 4.4 inches of rain for the month. It is also interesting to note that October marked the first month since July that the city received above-average rainfall.
Credit: The Weather Gamut