Timing: Here’s when heavy rainfall is forecast Wednesday afternoon and evening

Forecasters say urban flooding from the downfall could coincide with rush hour.

Boston, MA - 7/24/2017 - An umbrella-protected man crosses School Street in Downtown Crossing. The recent heat wave over, rain returns to the area. Photo by Pat Greenhouse/Globe Staff Topic: standalone rain DowntownCrossing Reporter: XXX Pat Greenhouse / The Boston Globe

You’ll want to keep your umbrella handy for the Wednesday evening commute.

The National Weather Service is forecasting heavy rain with the potential for “torrential downpours” in central and eastern Massachusetts and Rhode Island starting in the afternoon and continuing into the overnight hours. The service has issued a flash flood watch, which goes into effect starting 1 p.m.

“Given the potential for torrential rainfall to be impacting portions of the urban corridor, significant urban flash flooding is a concern which may also coincide with the evening rush hour,” meteorologists said

The precipitation is the result of a cold front interacting with Tropical Storm Erin, which is making its way up the Atlantic off New England, according to the service.