The National Weather Service has issued a Severe Thunderstorm Watch for Northern Virginia through 11 p.m. Tuesday.
A watch means conditions are favorable for a severe thunderstorm. Heavy rain, strong wind and hail are all possible.
After a day of near-record heat and a heat advisory (which will remain in effect until 7 p.m.), storms are expected to to hit Reston between 4 and 7 p.m., forecasters said.
With the humidity today, the heat index made it feel around 105 degrees outside.