First Day Of Fall Won't Feel Like It

It's the first day of fall, but Mother Nature doesn't seem to have gotten the memo.

Temperatures on Long Island will be in the 80s Monday and the heat index – how hot it feels with humidity factored in – is expected to top 90s on parts of the island. It will be "coolest" along the South Shore and the Twin Forks.

Thunderstorms are possible later in the day. Any rain should hold off until after sunset, the National Weather Service says. There's a chance of thunderstorms from about 8 p.m. until midnight.

If you are skipping out of work or school today to hit the beach, stay out of the water. Very strong rip currents will be dangerous to anyone who enters the surf.

The strangely warm weather will hit the same day that international leaders descend on New York City for the United Nations Climate Action Summit focused on combatting the climate change crisis. Thousands of youth marched through Lower Manhattan during Friday's Climate Strike protest ahead of the gathering.

The full Long Island forecast:

Monday- Mostly sunny, with a high near 82. Southwest wind 14 to 17 mph.

Monday Night- Showers and thunderstorms likely before 2am, then a chance of showers. Cloudy, then gradually becoming partly cloudy, with a low around 64. Southwest wind 6 to 14 mph. Chance of precipitation is 70%. New rainfall amounts between a quarter and half of an inch possible.

Tuesday- Sunny, with a high near 78. Northwest wind 9 to 13 mph.

Tuesday Night- Mostly clear, with a low around 56. Northwest wind 6 to 8 mph, with gusts as high as 20 mph.

Wednesday- Sunny, with a high near 75. West wind 6 to 10 mph.

Wednesday Night- Mostly clear, with a low around 62.

Thursday- Mostly sunny, with a high near 80.

Thursday Night- Mostly clear, with a low around 57.

Friday- Sunny, with a high near 74.

Friday Night- Mostly clear, with a low around 59.

Saturday- Mostly sunny, with a high near 80.