Airlines canceled more than 4,000 flights across the U.S. over the weekend as heavy snow and thunderstorms snarled operations at major airports in cities like Chicago and Dallas, leaving some travelers stranded overnight.

Storms dumped more than 5.3 inches of snow at Chicago's O'Hare International Airport on Sunday, prompting airlines to cancel more than 1,000 flights. Those that did take off Sunday were delayed by an average delay of 44 minutes, according to the Chicago Department of Aviation. Another 189 flights were canceled Monday morning at O'Hare, while travelers stuck overnight Sunday were still struggling to schedule their trips.

American Airlines said it canceled more than 1,700 flights due to the Chicago snowfall over the weekend and thunderstorms along the East Coast on Monday morning. Southwest has canceled more than 400 flights since Saturday.

Overall, more than 38,500 flights have been delayed since Saturday, and over 4,500 have been canceled, according to flight tracking site Flightaware.com.

Heavy rainfall and flash flooding will exit the Northeast later Monday, but threats of "severe" thunderstorms and some flash flooding will continue to spread across the eastern U.S. through Friday, the National Weather Service said.

After heavy snowstorms, Chicago temperatures are increasing and are expected to reach the mid-50s on Monday and the mid-to-high 60s by Tuesday, forecast models show.