The July 4 weekend heatwave has given way to heavy rain on Monday that has put the city under a flood watch, according to NYC Emergency Management (NYCEM).

The emergency management agency issued a travel advisory Sunday, warning residents of likely delays during Monday morning’s commute, with Mayor Zohran Mamdani urging people to avoid travel if at all possible.

“Now it’s time for all of us to do our part,” Mamdani said in a statement. “Limit travel if you can, plan for delays and take these warnings seriously. If heavy rain begins, if the winds pick up or if you hear thunder — get inside and wait out the dangerous conditions.”

Trains operated Monday morning with delays on the uptown B, D, and R lines, downtown 1 line, and the Manhattan-bound 7 line.

But weather radars suggest the heaviest rainfall and possible thunderstorms may happen later Monday afternoon. The flood watch remains in effect for New YOrk City until 6 a.m. Tuesday morning. Emergency Management also warned that strong wind gusts accompanying possible storms have the potential to down tree branches and create hazardous conditions with unsecured outdoor objects.

NYCEM encouraged those in the area to subscribe to the city’s emergency alert system, Notify NYC, for real-time notifications and create a plan for possible thunderstorms and flash flooding. 

“As we’ve seen in recent storms, flash flooding can develop quickly and create dangerous conditions with little warning,” said NYCEM Commissioner Christina Farrell.

NYCEM urged residents to have a plan in place:

Know your risk of flooding and make a plan for where to go in the event of rising water. Be sure to plan multiple exists from homes or buildings. 
Prepare essentials immediately including medications, medical devices, extra batteries and mobility devices. 
Do not swim or drive through rising waters or enter flooded train stations. Do not touch flood water as it could be contaminated.
Prepare for power outages
Do not wait to take action
If you’re in danger, call 911