Nor'easter brings heavy rain and strong wind gusts to Massachusetts this weekend

A rare September nor'easter is moving into Massachusetts tonight, and forecasters expect Saturday to be the worst day.

Forecasters are calling it a washout. The storm is slow moving. Rain and wind stick around through Sunday, and it won't fully clear out until early next week.

When it hits

Friday night: Rain starts on the Cape and South Shore this afternoon and reaches Boston after dark. Wind picks up overnight.
Saturday: The worst day. Heavy rain, strong wind and flooding on the streets.
Sunday: Lighter rain, but heavy bursts still pop up.
Monday: The storm slowly pulls away.

How much rain

Most of eastern Massachusetts gets 2 to 4 inches, and some spots near the coast could see more. Areas west of I-95 get less, closer to 1 to 2 inches.

That's enough to flood streets and underpasses, especially in the city. Don't drive through water if you can't see how deep it is.

How windy

This is the part that could knock out power. Trees still have all their leaves, which makes them catch more wind and come down easier.

Cape Cod, the Islands and Cape Ann: gusts of 50 to 70 mph
The rest of the coast, including Boston: gusts of 40 to 55 mph
West of I-95: gusts of 30 to 40 mph

The National Weather Service has a High Wind Warning for the coast and a Wind Advisory for inland areas. The strongest wind is Friday night through Saturday night.

The coast

There's a Coastal Flood Watch through the weekend. Saturday is also a full moon, which pushes tides higher than normal. Expect minor flooding around high tide Friday and Saturday nights, big waves and beach erosion.

What to do

Charge your phone and a battery pack tonight.
Bring in anything loose from outside, like patio furniture and trash barrels.
Check the MBTA and airport before you travel Saturday.
If you lose power, report it to Eversource or National Grid instead of assuming someone else did.

What to watch for: how bad the wind gets Saturday afternoon and evening. That's when outages are most likely, especially near the coast.