The sun may be out, but that doesn’t mean the water is fine.

The National Weather Service in Gray issued a “beach hazards” statement on Saturday, urging boaters in coastal Maine and New Hampshire to “use extreme caution” to guard against hypothermia.

Sunny weather and temperatures in the 70s “may cause people to underestimate the dangers of the cold water temperatures,” which are in the upper 40s to mid-50s, the warning said.

“The cold water temperatures can quickly cause hypothermia,” it said. “Anyone on boats or paddlecraft should use extreme caution to avoid this threat.”

Several people in small boats have drowned or died in accidents this spring, including incidents in Raymond, Fryeburg, Vassalboro and West Forks Plantation.

Cool, rainy weather has delayed the traditional Memorial Day start to the summer boating season.

Temperatures in Maine are expected to reach the 90s on Sunday.