It’s cold this week. Really cold.

Firefighters saw water freezing in their hoses as they fought a blaze south of Montreal Thursday night, and farmers in the upper Midwest are worried about the fate of their winter wheat crop.

The bone-chilling temperatures that have settled over the central and eastern US and much of Canada this week will likely last into 2018.

The National Weather Service forecasts wind chills around – 40 degrees Fahrenheit for much of the upper Midwest on New Year’s Eve.

And on Thursday, President Donald Trump kicked off a conversation that seems to happen every year around this time, with a tweet from his Mar-a-Lago resort in Florida.

In the East, it could be the COLDEST New Year’s Eve on record. Perhaps we could use a little bit of that good old Global Warming that our Country, but not other countries, was going to pay TRILLIONS OF DOLLARS to protect against. Bundle up! — Donald J. Trump (@realDonaldTrump) December 29, 2017

"In the East, it could be the COLDEST New Year's Eve on record," Trump tweeted.

"Perhaps we could use a little bit of that good old Global Warming that our Country, but not other countries, was going to pay TRILLIONS OF DOLLARS to protect against. Bundle up!"

The tweet quickly drew reactions from exasperated lawmakers, climate scientists and meteorologists annoyed at the continued conflation of short-term weather conditions and longer-term climate trends.

In 2017, there were about three record high temperatures in the U.S. for every record low temperature. Weather is not the same as climate. The president should be able to understand that. It isn't hard. https://t.co/piwHcvZWbH https://t.co/7EFkR5SmUN — Rep. Pramila Jayapal (@RepJayapal) December 29, 2017

A region’s climate refers to the average weather conditions that prevail there, and can be studied by climatologists looking at long-term historical trends.

Weather varies day to day.

“Climate is what you expect,” says NBC Miami meteorologist John Morales, “and weather is what you get.”

As Morales pointed out in his TV broadcast Thursday, even though much of North America is experiencing below-average temperatures this week, most of the rest of the world is warmer than usual right now.

“It’s pretty mild to downright very warm as compared to normal, with the warmest readings in the poles, both North and South,” Morales tells The World in an interview. “Really the only pocket of very cold air, compared to averages, is across North America.”

Temperatures across most of the world are higher than the historical average. North America, swathed in blue, is the exception. Credit: University of Maine Climate Change Institute

President Trump used the phrase “global warming” in his Thursday tweet, a term that’s fallen out of style among scientists and environmentalists because it doesn’t reflect the many changes expected as carbon pollution alters the climate: more intense rainfall, increasing drought, rising sea levels, and other changes that vary from region to region.

The current cold snap is a result of a southward dip of the jet stream, bringing icy Arctic air into Canada and the US.

Some studies do suggest that climate change will shift the jet stream’s patterns and may bring these cold days to parts of the US more frequently — but that point is still being studied and debated.

“That portion of climate science is not settled yet — many peer-reviewed papers indicate that might be happening in the future — there are other peer-reviewed papers that indicate those are cyclical changes in terms of the orientation of the jet stream,” Morales tells The World.