Frost Advisory, Freeze Warning Issued for Long Island

Temperatures set to plunge, putting tender plants at risk

Apr. 20, 2026 at 9:43am

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A sweeping, atmospheric landscape painting in muted tones of blue, grey, and white, capturing the overwhelming scale of a frozen, snow-covered field under a dramatic, cloudy sky. The scene conveys the raw power of the natural world, with any physical structures or objects dwarfed by the overwhelming weather conditions.A sudden cold snap brings the threat of frost and freeze conditions, putting Long Island's delicate spring growth at risk.Commack Today

The National Weather Service has issued a frost advisory for Suffolk County and a freeze warning for both Suffolk and Nassau Counties on Long Island, with temperatures expected to drop below freezing overnight into Tuesday morning. The cold conditions could kill crops and other sensitive vegetation, prompting the NWS to advise residents to take steps to protect tender outdoor plants.

Why it matters

Sudden drops in temperature can pose a serious threat to local agriculture and landscaping, especially during the spring season when new growth is vulnerable. Frost and freeze events can devastate crops, damage plants, and disrupt the local ecosystem if proper precautions are not taken.

The details

The frost advisory for Suffolk County is in effect until 8 a.m. on Monday, with temperatures as low as 33 degrees expected to result in frost formation. The freeze warning, meanwhile, remains in effect from midnight until 9 a.m. on Tuesday, with sub-freezing temperatures as low as 27 degrees forecast. While the freeze watch has been lifted in Nassau County, temperatures there are still expected to hover around the freezing mark.

  • The frost advisory for Suffolk County is in effect until 8 a.m. on Monday, April 20, 2026.
  • The freeze warning for both Suffolk and Nassau Counties is in effect from midnight until 9 a.m. on Tuesday, April 21, 2026.

The players

National Weather Service

The National Weather Service is the primary source of weather data, forecasts, and warnings for the United States.

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What’s next

Residents in the affected areas should take steps to protect any tender outdoor plants, such as covering them or bringing them indoors, to prevent damage from the expected frost and freeze conditions.

The takeaway

This sudden cold snap serves as a reminder that even in the spring, Long Island's weather can be unpredictable and potentially harmful to local agriculture and landscaping. Staying vigilant and taking proactive measures to protect vulnerable plants is crucial during these types of weather events.