And just like that, ice is gone from Lake Winnipesaukee almost before we knew it was there.

On Sunday, the earliest ever “ice-out” was declared on the lake, just 37 days after the latest ever “ice-in” was declared Feb 9.

The declarations are unofficial, made by pilots at Emerson Aviation in Gilford, but they’re a widely accepted measure of how winter is going in New Hampshire. This year it hasn’t gone well, with events from dogsled races to outdoor ice hockey to “pond skims” at ski areas curtailed or canceled due to early spring. As the climate changes that’s going to happen more and more often.

Winnipesaukeeisn’t alone, of course. Startling rises in ocean temperatures around the world are leading to predictions that virtually the entire Arctic Ocean could be ice free this summer, an unprecedented event in human history.

Ice-in means most of Lake Winnipesaukee is frozen, while ice-out only means the MS Mount Washington boat can make it to its five ports of call and navigate around its usual route. Ice-out has been called for more than a century by different people but ice-in has only been declared for a little over a decade.