Long Islanders could feel the year’s first muggy heat wave to start the week, forecasters say.

Before that, though, Saturday is looking to be a great day to hit the beach or the Belmont Stakes before it starts to feel like a scorcher on Sunday.

Saturday is expected to be partly sunny, with a high near 81, according to the National Weather Service. There will a “light south wind” becoming southwest at 8 to 13 mph in the morning.

“For the Belmont Stakes, it will be a fair day overall. We will see the chance for a stray shower or two through the day up until around the main event this evening,” News 12 Long Island meteorologist Matt Hammer said. “This could at worst make for damp track conditions, but should not impact the race more than that.”

Those heading to the beach should know that a high rip current risk is in effect for Suffolk’s ocean beaches through 9 p.m. Saturday. Swimmers caught in a rip current should not swim directly for shore, but are advised instead to swim parallel to the shore to get away from the swift-moving waters.

Saturday night is mostly clear with a low of about 67, the service said.

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Sunday brings more sunny weather — with high temperatures expected to touch the 90s in parts of Nassau and western Suffolk counties, with highs in the 80s for the rest of the Island, the service said. Temperatures of at least 90 degrees for three consecutive days would be considered a heat wave.

Warm temperatures are expected to be accompanied by high humidity that will make it feel even hotter than what appears on the thermometer, weather service meteorologist John Murray said.

“The humidity will be a factor,” Murray said. “It’ll feel increasingly humid tomorrow into early next week.”

Western Long Island is forecast to see highs in the 90s starting Sunday through Tuesday, with the East End ranging in highs from the low to mid-80s.

High temperatures for most of Long Island are expected to cool to the low to mid-70s by the end of the week.

The region should remain relatively dry, with only a slight chance of thunderstorms Tuesday night and Thursday night into Friday.