Severe thunderstorms could dump up to 4 inches of rain per hour this evening in the nation’s capital and parts of Howard and Anne Arundel counties, the National Weather Service warned Saturday.

The storms are forecast to start around 6 p.m. said Kevin Rodriguez, lead meteorologist for the Baltimore-Washington region, shortly before a military parade celebrating the 250th anniversary of the Army is set to begin amid nationwide “No Kings” protests.

“Our main concern is the heavy rainfall that leads to flash flooding,” he said.

Rodriguez said he expects heavy showers to start Saturday afternoon around Hagerstown and Frederick and progress south and east throughout the afternoon. The threat is greater because the ground is saturated from rain that fell Friday. Lightning and isolated bursts of high winds are also forecast.

Although the storm system could pass through Southern Baltimore, most of the city is expected to escape the worst of the weather, he added.

“If we see 4 inches of rain in an hour, that poses an extreme risk of flash flooding,” Rodriguez said.

The Maryland Department of Emergency Management issued a flood watch for Anne Arundel, Carroll, Frederick and Washington counties until 11 p.m. Saturday.

Some area events are being canceled in anticipation of the storms. The eighth annual Baltimore Flotilla was called off “out of an abundance of caution” for the safety of participants, partners and media.

In addition to storms, Harford and Baltimore County fire officials warned residents of hazy skies and the smell of smoke from wildfires in Canada and New Jersey, and vulnerable people should limit time outdoors.

Highs on Saturday will be lower than the day before — around 80 degrees.

It’ll be even cooler on Father’s Day. Prepare for highs only in the upper 60s to low 70s Sunday afternoon.

Sunday also brings its own rain chance. The upcoming workweek doesn’t look to completely dry out until closer to AFRAM weekend.

Enjoy the break from the heat because the region is expected to see extreme temperatures in the coming days.

The strongest heat wave of the season thus far is likely for much of the mid-Atlantic during the first week of summer, according to the National Weather Service. The affected cities include Washington, Baltimore, Philadelphia, Richmond, Virginia; and Raleigh, North Carolina.

WJZ is a media partner of The Baltimore Banner.