Overnight lows were forecast in the lower 60s.
Clouds are expected to gradually increase overnight Friday, bringing a slight chance of showers from early Saturday morning through the weekend and into early next week. Rain chances are estimated at about 20 percent during the day Saturday and 40 percent in the evening and overnight.
About a quarter of an inch of rain is possible Saturday, according to the weather service. Highs are expected in the mid-70s, with lows in the upper 50s.
A southerly flow of moist air is expected in the East, but it's unclear if rain showers will drift north of Virginia, according to a National Weather Service forecast discussion posted Thursday afternoon.
It would be the first time in at least five years that it rained on Preakness, according to weather service data.
Rain chances increase Sunday, at about 60 percent, with highs around 70 degrees and lows in the mid-60s. Rain and storm chances continue Monday and Tuesday.