Long Island's weather on Friday is expected to feature sunny skies and pleasant summerlike temperatures, but also some nasty air pollution.

On Thursday afternoon the state Department of Environmental Conservation issued an air quality alert for Friday from 11 a.m. to 11 p.m. for both Nassau and Suffolk counties.

An air quality index higher than 100 is predicted for ground-level ozone.

The index for Long Island on Thursday afternoon was only 48, but for New York City it was already 101.

When the index is elevated, the state Health Department recommends that individuals consider limiting strenuous outdoor physical activity to reduce the risk of adverse health effects. People who may be especially sensitive include the very young, and those with preexisting respiratory problems such as asthma or heart disease.

Aside from the air quality, once patchy fog clears by about 8 a.m., Friday's weather looks good. The National Weather Service predicts it will be mostly sunny with a high near 78 degrees and a light west wind shifting to coming out of the south at 5 mph to 10 mph in the afternoon.

Friday night there is a chance of showers and thunderstorms. After 2 a.m., showers will be likely and a thunderstorm will be a possibility. The chance of precipitation is 60%.

The weather service's area forecast for Friday said, "Ahead of an approaching back door cold front, a pre-frontal trough develops and moves in for the afternoon. Clouds and eventually some showers and thunderstorms develop in the afternoon."

On Saturday showers are likely and a thunderstorm is possible before 8 a.m. followed by a chance of showers through the day as the chance of precipitation is again 60%. The high temperature should be near 66 degrees.

On Sunday there is a 30% chance of showers before 8 a.m., and then mostly sunny with a high near 68 degrees, according to the weather service.

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