4TH MAY STAR NATURE’S FIREWORKS: LIGHTNING

Thunderstorm risk predicted for afternoon but clearing by evening.

If you’re planning to venture outdoors for the Fourth of July holiday, fire up the grill early, pack some sunscreen — and bring an umbrella.

High temperatures near 90 degrees are forecast for today and Wednesday, along with thunderstorms in the afternoon, according to the National Weather Service in Miami.

Scattered showers and thunderstorms are expected today, with the weather service predicting a 30 percent chance of rain. For the Fourth of July, there will be a 50 percent chance of rain in Palm Beach County, mainly in the afternoon, the weather service said.

Showers and thunderstorms are forecast to develop along the east coast and move inland, toward the Gulf Coast. The rain showers, however, should clear in time for evening fireworks displays planned for various locations across the county.

“This time of year, being the rainy season, there is a chance of thunderstorms,” said Robert Molleda, warning coordination specialist for the National Weather Service. “That’s at the top of the list (of things to be mindful of ). ... If you hear thunder, it’s time to go indoors.”

The thunderstorm activity will bring a moderate risk of lightning. There have been four lightning-related deaths across the state this year, and July and August are typically the most dangerous months in Florida.

Martin County authorities believe that lightning may have been a factor in a fire that damaged four construction vehicles at a construction company’s compound Sunday in Indiantown.

“Be aware of weather wherever (you are),” Molleda said. “If you hear thunder, it’s time to go indoors.”

There will be a slight risk of rip currents for South Florida’s beaches. But Molleda cautions that beach-goers should still take precautions and swim in areas near lifeguards.

“Even on slight risk days, there still could be some currents, especially near inlets,” he said. “So people do have to be cognizant of that.”

While hot temperatures are expected across South Florida, those traveling for the Fourth of July holiday could experience even hotter temperatures as a heat wave continues to grip parts of the Northeast and Midwest.

Major cities such as Washington, D.C., Philadelphia and New York City had heat index values near 100 degrees Monday.

An excessive heat warning — a heat index of 105 degrees lasting two hours or more — is in effect through this evening for Philadelphia, forecasters said.

Today’s high will be near 93 degrees for Washington, D.C. and Boston, and 90 degrees for New York City.