Hummingbirds in my area (central Kentucky) are strictly warm weather birds, arriving in mid to late June, and staying until the end of August, or until the first cool nights send them south to a warmer climate. As ruby-throated hummingbirds are the only species of the bird east of the Mississippi River, I'm sure that the same conditions apply in Maryland, where your weather is very similar to ours.
Hummingbirds in my area (central Kentucky) are strictly warm weather birds, arriving in mid to late June, and staying until the end of August, or until the first cool nights send them south to a warmer climate. As ruby-throated hummingbirds are the only species of the bird east of the Mississippi River, I'm sure that the same conditions apply in Maryland, where your weather is very similar to ours.