Good morning on this cheery-chilly Thursday.

It’s a slap in the face.

The weather, we mean.

It’s become very chilly, very fast. We’ll have lows in the 30s today, and it won’t climb much above 50. Tomorrow will be even more shiver-inducing, with lows in the 20s and a high in the 30s. (More of the same on Saturday. Wince.)

Part of it is “shock value,” said John Homenuk, the founder of New York Metro Weather, because New York has had such a warm season. But even so, what we’re seeing now is about 15 degrees colder than normal for this time of year, Mr. Homenuk said.

Even when we’ve had a day or two of cooler weather during this so-called “hotumn,” things have quickly rebounded to normal or warmer-than-normal. But the intense cold rolling in for the weekend “is not something that we’re going to snap back out of,” Mr. Homenuk said.

Temperatures for the next two weeks will likely average below normal, he told us, and they’re expected to remain near or below average through the end of November. “It won’t stay that cold every single day, but the pattern is really changing.”