Sunday’s hazy, hot and humid weather marked the fourth day of a heat wave on Long Island in which high temperatures broke records, with the National Weather Service issued warnings of “dangerous” conditions for Long Island and New York City.

But a cold front moving into Long Island will make sure Monday’s weather won’t extend the heat wave, forecasters said.

The upcoming week will bring “some relief from the heat,” but highs will still be above average, said National Weather Service meteorlogist Joe Pollina said.

Sunday, the service issued an excessive-heat warning for Nassau County and southwestern Suffolk, and a heat advisory for northeastern and southeastern Suffolk. Both were in effect until 10 p.m. Sunday, while New York City’s heat warning is in effect from noon to 8 p.m. Monday.

“It’s unprecedented to have a heat wave in this part of August,” News 12 Long Island meteorologist Justin Godynick said Sunday.

A heat wave is at least three consecutive days of 90-degree temperatures or above. In Islip, a high of 97 degrees Sunday broke a record of 89 degrees for that day last set in 2005. For this time of year, the normal highs are in the low 80s, said Pollina.

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Sunday’s warm overnight lows in the middle to upper 70s also came with showers in some areas, ushering in the cold front that will keep temperatures in the high 80s Monday.

Mostly sunny skies are ahead for Tuesday, where there’s a chance of showers and a thunderstorm. Highs are expected in the upper 80s and lows in the mid-70s, Pollina said.

On Wednesday, there’s another chance of a thunderstorm, with highs in the upper 80s and lows in the mid-70s.

Sunnier skies return for Thursday, with highs in the upper 80s and lower 70s expected at night.

Cooler temperatures will continue into Friday, with highs in the lower 80s, and lows in the upper 60s expected at night.