For the latest on the winter storm, read Wednesday’s live updates.

John Schwartz, a New York Times reporter who covers climate change and the environment, is answering reader questions about the winter storm in the Northeast United States, the second to hit the region in less than a week. Ask your questions about the causes of dangerous winter storms by emailing storms@nytimes.com.

If it’s cold, how can there be climate change?

That’s a common question — one asked, in various ways, by the president of the United States. But it’s based on a fallacy.

Weather is not climate. Weather refers to day-to-day conditions; climate is about long-term trends. And the long-term trends show a planet that is warming, especially in the Northern Hemisphere. Even with occasional Arctic blasts of bitter cold, which we’ve seen in much of the United States in recent years, 2017 had the second-highest surface temperatures ever recorded, surpassed only by 2016 — which was the third “hottest year” in a row. The trends are clear, even if you can make a snowball in March in Central Park.

Really, though — is there some connection between climate change and this cold weather?

Scientists have been looking at phenomena like cold spells, which occur when air from the Arctic dips south. After all, the Arctic is warming as a result of climate change, and that appears to be weakening the jet stream, which tends to hold that cold air up toward the top of the world. As Marlene Kretschmer, a researcher at the Potsdam Institute for Climate Impact Research in Germany, told The Times in January, the connection is not yet fully established. “There’s a lot of agreement that the Arctic plays a role, it’s just not known exactly how much,” she said. “It’s a very complex system.”