Rainfall Outlook and Hurricane Erin: Technical Forecast Discussion Issued: August 20, 2025

Matthew Moll
Aug 20
2 min read

Rain First, Then Clearing

Rain is moving into New England today and will be with us into Thursday morning. For most of the region, it’s scattered showers. But in southern New England — Connecticut, Rhode Island, and southeastern Massachusetts — the rain will be steadier and heavier, adding up to 1–1.5 inches before tapering off by mid-morning Thursday.

Northern and central New England will see less rain, closer to a half inch or less, with the bulk falling overnight. The morning commute in Boston and Providence could be slow thanks to some localized ponding on roads.

And again — this rain isn’t from Hurricane Erin. It’s from a separate front sweeping through.

Hurricane Erin’s Update

Now, about Erin. The storm is sitting offshore as a Category 2 hurricane with winds in the 95–100 mph range. Guidance keeps showing a slightly westward track, meaning the storm is closer to the East Coast than earlier forecasts suggested, but still not making landfall.

North Carolina’s Outer Banks (Cape Hatteras) is already under a mandatory evacuation because of flooding, even though Erin’s center stays offshore. The storm should hold Cat 2 strength into the weekend before weakening as it encounters cooler waters.

*The latest National Hurricane Center cone, showing Erin staying offshore but uncomfortably close for the Mid-Atlantic coast.*

Ocean Impacts Here in New England

Even though Erin won’t bring us rain or wind, the ocean tells another story.

Wave heights: Seas are already 7–10 feet south of New England. By Thursday, they’ll build to 14–16 feet, and by Friday into Saturday those big swells push up into the Gulf of Maine.
Rip currents: The risk is high right through Sunday. If you’re thinking about swimming in the ocean — don’t.
Boating: Harbor masters along Cape Cod, the Islands, and coastal Maine are strongly recommending people haul boats out of the water or at least tie them up in safe harbor until conditions calm down.

*WaveWatch III output shows wave heights building Thursday and peaking Friday into Saturday across the Gulf of Maine.*

Why Erin Stays Offshore

So why doesn’t Erin turn inland? The steering setup is key. A ridge over the Mid-Atlantic and a trough over the Great Lakes are keeping Erin on a northeast track, running parallel to the coast. Both the GFS and European ensembles keep it offshore, with no sign of a direct hit. The storm simply rides the boundary, then weakens over cooler waters as it moves out to sea.

Bottom Line

Rain: Scattered today and tonight, tapering off Thursday. Heaviest totals south (CT/RI/SE MA).
Erin: Stays offshore, remains a Cat 2 for a couple more days.
Coastal impact: Big waves, dangerous rip currents, and hazardous boating conditions through Sunday.

If you’re inland, this week’s story is rain tonight and a nice break by the weekend. If you’re near the water, the story is the ocean — stay off the beaches and play it safe with boats.

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