Beware of the cold water this holiday weekend, even if the air is warm, the National Weather Service is cautioning.

Although the air temperature will rise into the 70s across the region, the water temperature will be in the 50s — and that can pose an extreme risk, the weather service said in the run-up to Memorial Day weekend, the unofficial start of the summer season.

“The cold water temperatures can quickly cause hypothermia to anyone immersed in the water. When the water temperature is below 60 degrees, the average submerged person could lose dexterity within minutes and be unable to accomplish simple tasks,” the weather service wrote in an advisory Saturday morning.

“Anyone on small boats, canoes or kayaks should plan accordingly if recreating this weekend, and use extreme caution to avoid this threat.”

On Long Island, skies are forecast to be sunny, with a high near 75 degrees both Saturday and Sunday, dropping to nighttime lows around 53 Saturday and 55 Sunday.

Monday will be warming — a 77-degree high and a 54-degree low.

It'll be mostly sunny on Sunday and Monday during the day.

Newsday LogoCovering LI news as it happensDigital AccessOnly 25¢for 5 months