The National Weather Service is predicting an afternoon high Monday of 78 degrees at BWI-Marshall Airport. That's not a record. But Sterling pretty regularly underestimates high temperatures for Baltimore, so there's a good chance the airport will see something more than 78.
The record for Baltimore on an April 4 is 83 degrees, set in 1956. It just happens to be the lowest daily high-temperature record on the books for April, so it's low-hanging fruit.
The forecast calls for mostly sunny skies today. The April sun is strong, so provided clouds don't dim the afternoon rays, we could well slip into the low 80s for the second time this year. The first, you'll recall, was the record high of 81 degrees, reached on March 18.