MA Weather: Severe Weekend Storm Timeline, Tornado Threat

You know it's supposed to rain tonight, it's supposed to rain a lot, and it's supposed to rain for quite some time. But do you know where and when? The National Weather Service offered some hints as to when you can expect this weekend's tropical downpours.

The heavy rain - we're talking between 1-2 inches per hour with local totals of perhaps more than 3 inches - starts around 10 p.m. Saturday and goes until 5 p.m. Sunday. It will be particularly strong between 3-10 a.m. Sunday. It will continue to rain on and off into the evening with some impacts lingering into Monday. See the simulated radar below.

The thunderstorms could be severe, and there's even a slight chance of a tornado.

"The potential threat of a brief spin-up of a tornado / waterspout definitely exists around early Sunday morning," the NWS said, noting that the Concord tornado of 2016 and Revere tornado of 2014 occurred on Sunday mornings.

Sunday will kick off a trend of humid rainfall that is expected to be a major theme this week.