Long Islanders should begin preparing for the upcoming Atlantic hurricane season with emergency to-go kits of necessary supplies and developing evacuation and sheltering plans, Nassau County Executive Edward Mangano and Suffolk County Executive Steve Bellone said Thursday.

While the National Oceanic and Atmospheric Administration has forecast a lighter-than-normal hurricane season, which runs June 1 through Nov. 30, officials advised residents to be vigilant and prepare for the worst.

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"Just one storm can cause significant harm to our residents and the assets we have here in the county," Mangano said at a news conference in Mineola.

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Bellone said that despite projections of a milder storm season, residents must "be prepared because you don't know what may come."

David Daly, president and chief operating officer of PSEG Long Island, said the utility has improved its communications systems since superstorm Sandy in 2012. He said the company is better equipped to share information about outages with customers, municipalities and first responders.

"While we hope to never again see a storm like Sandy, we know that past experiences have taught us to expect the unexpected," Daly said.

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Officials said emergency to-go bags should include five days worth of supplies, including a first-aid kit, medicine, a change of clothes, a battery-powered flashlight, a radio and a waterproof container for important documents.