Sign up for our COVID-19 newsletter to stay up-to-date on the latest coronavirus news throughout New York Parts of western Long Island may get on Monday the third straight day of sweltering temperatures of 90 degrees or above, the unofficial threshold to qualify as a heat wave, forecasters said.The heat streak came as the National Weather Service (NWS) issued a heat advisory from noon to 8 p.m. Monday for Nassau and western Suffolk counties as well as much of the New York Metro area. That’s because temps in the 90s combined with the humidity will make it feel like about 100 in some areas.“It’ll be a close call,” Bill Goodman, an Upton-based NWS meteorologist, said of the heat wave designation.Temps at Long Island MacArthur Airport in Ronkonkoma hit 96 on Saturday and 90 on Sunday, but were only forecast to hit 88 on Monday. Goodman predicted that temperatures may rise into the 90s in parts of Nassau.Thermometers fell two degrees short of 90 Friday on LI, but New York City is on its fourth straight day of temps in the 90s.A 20-percent chance of thunderstorms forecast for Monday afternoon on LI are not expected to provide any relief. Tuesday is expected to hit the low 90s on LI, but the humidity won’t be as high so the heat index won’t be as bad, Goodman said. The region should get a break with temps in the 80s Wednesday through the weekend.As for the heat advisory, NWS warned that the elderly, those with chronic health issues and those whose homes lack air conditioning should go to a place that has air conditioning. It also urged people who work outdoors to take frequent breaks in the shade or in an air-conditioned area.NWS also issued an air quality alert for all of Long Island due to increased ozone pollution levels. And anyone cooling off at the beach is warned that there is also a risk of rip currents.