Heavy rains and wind knocked out power to more than 20,000 National Grid customers Tuesday, with Rensselaer and Saratoga counties taking the brunt of a nasty afternoon storm that came with tornado threats and reports of large-scale flooding.

Nearly 9,000 customers in both Rensselaer and Saratoga counties lost electricity, according to National Grid, which also said that some 2,000 homes and businesses in Schenectady County and 977 in Albany County had no power at around 6:30 p.m.

The storm in Saratoga Springs caused trees to fall on power lines at Union Avenue and Circular Street and other locations, and brought road closures and power outages across the western part of the city. Police asked city residents to avoid driving.

"The entire city got hit hard," Saratoga Springs Police Lt. John Catone said. "It was mostly heavy rains and high winds."

By 9:30 p.m., a total of about 10,000 customers in the four counties were without electricity. Power had returned to most of Saratoga Springs, and there were no injuries reported.

Motorists reported heavy flooding on Route 9 in Latham and other locations. Parts of Route 43 in North Greenbush were still closed late Tuesday due to a downed tree.

The National Weather Service had issued a tornado warning for parts of Fulton, Hamilton and Herkimer counties, and similar warnings for a twister were issued in Warren and Washington counties. The weather service issues a tornado warning if a tornado strike is imminent. While no evidence of tornados were reported, severe thunderstorms pounded Saratoga County and other parts of the region starting at about 4:45 p.m.

The less intense tornado watch was issued earlier for a large portion of eastern New York including the Capital Region and the Adirondacks. Hail was reported in Warren County.

In Albany a tree fell at North Pearl and North First Street, closing the road while it was removed.

"The atmosphere's got a lot of energy today because of heat and humidity," National Weather Service Meteorologist Ray O'Keefe said Tuesday.

O'Keefe said the combination of the atmosphere's heat and humidity combined with an approaching cold front that promised strong thunderstorms and spinning winds from the Hudson Valley made the conditions right for a tornado.

"Thunderstorms lift it up and create a tornado," he said.

The watch was issued for a wide area stretching from Greene and Columbia counties to the Canadian border. It also included all of Vermont and Berkshire County in Massachusetts.

Meteorologists are constantly watching the radar, O'Keefe said, and if the spin in the winds picks up, a warning would be issued.

"If we issue a warning, you have 10 minutes tops," hydrologist Britt Westergard said.

The severe weather won't immediately bring any relief to the daytime heat and humidity. Though overnight lows will dip into the mid 60s, temperatures are expected to climb into the mid 80s Wednesday, Weather Service meteorologist Warren Snyder said. The summer-like weather will move out of the area Thursday, when highs will only hit the mid 70s, Snyder said.

"It's going to be a very gradual cool down," Snyder said.

Average highs for this time of year are typically in the mid to low 70s, Snyder said. Tuesday's high in Albany was 91. It's expected to reach about 82 degrees Wednesday.

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