NEW: The National Weather Service has issued a "frost advisory" for Nassau County from 11 p.m. tonight until 9 a.m. Thursday. Protect any sensitive plants and vegetation with temperatures dropping down into the lower to middle 30s tonight. This applies to both Nassau and Suffolk Counties even though there is not a frost advisory for Suffolk County. The reason for this is that the official growing season begins on April 11 in Suffolk, while it started on April 1 in Nassau County. Frost and freeze advisories, watches and warnings directly correlate to agricultural and infrastructure protection.

Into this evening: After a very chill start, Long Island will continue to feel chilly despite plenty of sunshine today. Afternoon temperatures will only reach the mid to upper 40s, which is about 10 degrees below normal for this time of year. The air remains dry, and while it won’t feel as harsh as the overnight cold, it will still be a noticeably cool day across the island.

Tonight into early Thursday morning, temperatures will drop again under clear skies. Many inland and sheltered areas could fall into the 20s, while coastal spots stay a bit milder but still quite cold for April. Dry and quiet weather continues through Thursday, with temperatures slowly rising but still running slightly below average. There could be areas of frost around as southeast winds will bring in some Atlantic moisture tonight.

By Friday, a warming trend begins to take hold. Highs will climb into the mid-50s to low 60s across Long Island. A cold front passes early Saturday, but it won’t have much impact on temperatures. The weekend stays mild, with highs generally in the mid-50s to mid-60s and no major weather concerns.

Looking ahead, a much bigger warmup arrives early next week. Temperatures will reach the 60s on Monday and then climb into the upper 60s to low 70s by Tuesday and Wednesday. That’s well above normal for April and will bring a much more springlike feel to Long Island after the midweek chill.