Long Island weather: Heat advisory for parts of Long Island, no relief till the weekend. 

Heat and humidity will define the weather Wednesday and Thursday, as the sun blazes forth and a cloud-clearing high pressure system pushes off to the north, the National Weather Service warned.

A heat advisory has been issued from noon Wednesday to 8 p.m. Thursday for Western Long Island. Such advisories are issued when heat indexes, which measure how the combination of heat and humidity will feel, top 95 for two days in a row.

The heat index will be between the mid and upper 90s Wednesday and even up to 100 Thursday. The rest of Long Island, while not in the advisory area, will still feel like it's in the 90s both days.

An air quality alert has also been issued by the weather service for all of Long Island from 11 a.m. to 11 p.m. Thursday.

The state health department, as a result, recommends limiting outdoor activity, especially seniors, young children and those with respiratory issue.

At least it will be a fine late summer day at the beach as, the weather service said, "Coastal areas may be a few degrees cooler with sea breeze activity and southerly flow by (the) afternoon."

During the day Friday, the weather service warned, it could be another sizzling day for New York City and northeast New Jersey as there is the potential for heat indexes to top 95.

But there is a 20% change of storms Friday night as a cold front approaches the region, dropping temperatures back into the high 70s for the weekend, with chances of showers both days

Cooling centers open in Nassau

With the heat advisory in effect, Nassau County Executive Laura Curran announced Wednesday that three cooling centers and charging stations would be open through Friday. Nassau also extended pool hours at two places.

Suffolk does not have county cooling centers and residents instead are asked to contact their local town governments for cooling center information.

These are Nassau's cooling centers and charging stations:

• Cantiague Park Administration Office, 480 W. John St. in Hicksville. Open from 10 a.m. to 8 p.m. Call 516- 571-7058
• Mitchel Field Administration Building Community Room, 1 Charles Lindbergh Blvd. in Uniondale. Open 10 a.m. to 6 p.m. Call 516-572-0400
• Wantagh Administration Building, 1 King Rd. in Wantagh. Open 10 a.m. to 6 p.m. Call 516-571-7460

Pools with extended hours are outlined below:

• Wantagh Park Pool, 1 King Rd. in Wantagh. Extended through Friday from 11 a.m. to 7 p.m.
• Cantiague Park Pool, 480 W. John St. in Hicksville. Extended through Friday from 11 a.m. to 7 p.m.

County pools are open seven days a week.

Cooler temperatures, storms possible

Temperatures should retreat over the weekend, falling to the high 70s during the day under mostly sunny skies — but the humidity again will be troubling and a few storms may sweep in.

A high pressure system likely will slide offshore on Saturday and Sunday, and its breezes will push "this moisture and associated warm front back into the region providing the focus for the potential for showers and thunderstorms," the weather service said.

Monday and Tuesday, when daytime highs should reach the low 80s, share the same 30% odds of rain and storms, the weather service added.