Boston weather and climate guide

7-day forecast for Boston

Tonight in Boston, MA brings mostly clear. Across the 8-day outlook, highs average 81°F and lows average 64°F, ranging from 61°F to 85°F. 2 of the 8 days carry at least a 30% chance of precipitation, so keep rain gear handy.

Current conditions

Observed at Boston, Logan International Airport (KBOS) at 8:30 PM EDT.

Nor'easters

The nor'easter is New England's signature storm, and the name refers to the wind direction, not the storm's movement. These are extratropical cyclones that develop or intensify along the East Coast, typically tracking northeast while their counterclockwise circulation drives strong winds onshore from the northeast.

They form when cold continental air meets the warm Gulf Stream offshore. That temperature contrast is sharpest from November through March, which is when the strongest nor'easters occur. A well-developed nor'easter combines heavy precipitation, sustained gale-force wind, coastal flooding at high tide, and beach erosion — often over 24 to 48 hours rather than the few hours a thunderstorm lasts.

When a nor'easter deepens rapidly, meteorologists call it bombogenesis: a pressure drop of at least 24 millibars in 24 hours. The Blizzard of 1978 remains the reference event, dropping over 27 inches on Boston, stranding cars on Route 128 and closing the region for a week. The January 2015 storm and the January 2018 event both produced blizzard conditions plus record coastal flooding in the Seaport district.

The rain-snow line problem

This is the single reason Boston winter forecasts change so often. The Atlantic stays far warmer than the land in winter, and coastal storms pull marine air inland. The boundary between snow and rain frequently sets up within twenty miles of downtown.

A storm track fifty miles offshore delivers a foot of snow to the city. The same storm tracking fifty miles inland delivers cold rain downtown and a foot to Worcester. That difference is often not resolvable until twelve hours out, which is why forecasters here talk in ranges and scenarios more than in single numbers.

Elevation compounds it. Worcester, 40 miles west at about 480 feet, averages roughly 60% more annual snow than Boston. Within the metro area, the western suburbs regularly get several inches more than the coast in the same storm. When a forecast gives a spread of three to twelve inches, it is not hedging lazily — the physical uncertainty really is that large.

Coastal flooding is a growing problem

Much of central Boston — Back Bay, the Seaport, parts of the North End — sits on land filled in during the nineteenth century, at low elevation. Combine that with Massachusetts Bay's substantial tidal range and nor'easter storm surge, and flooding does not require a hurricane.

Sea level in Boston Harbor has risen roughly a foot since 1920, and the rate has accelerated. The practical consequence is that a routine nor'easter arriving at astronomical high tide now floods streets that stayed dry under the same meteorological conditions decades ago. January 2018 produced the highest tide ever recorded in Boston Harbor and put seawater into Seaport streets and subway entrances.

The forecast language to watch is the combination of a coastal flood warning and the time of high tide. A moderate storm at high tide does more damage than a strong storm at low tide.

Hurricanes reach New England

Less often than the Southeast, but the events that do arrive are memorable. The 1938 New England Hurricane struck without meaningful warning, killed hundreds, and drove surge far up Narragansett Bay into downtown Providence. Hurricane Bob in 1991 and Sandy in 2012 both caused substantial regional damage.

Storms reaching this latitude are usually transitioning to extratropical systems, which changes their character: the wind field expands, the strongest winds spread away from the center, and rainfall becomes widespread rather than concentrated. That transition means a weakening storm can still be extremely dangerous over a broad area. Peak risk is late August through September.

Summer, and the sea breeze that ruins beach plans

July averages 82 °F with high humidity and enough heat waves to matter, particularly in a city with old housing stock and limited air conditioning in triple-deckers. Heat waves here are typically shorter than in the Midwest but the buildings hold heat.

The sea breeze is the local feature worth understanding. On a sunny day, land heats faster than water, air rises over the land, and cooler marine air flows in to replace it. The effect can drop coastal temperatures 15 to 20 °F in an hour while inland areas stay hot. It is why the forecast can call for 90 and Revere Beach sits at 68 with fog.

Fall is the region's best season without much argument: highs in the 60s and 70s through October, low humidity, clear air, and the foliage. The peak color window in the Boston area is generally mid to late October, running earlier at higher elevations and farther north.

Weather hazards to know about

• Nor'easters and blizzards

  November through March

  Heavy snow or rain, sustained gale-force wind, coastal flooding and multi-day duration. The defining regional storm.

• Coastal flooding

  Year-round, worst in winter storms

  Filled low-lying land plus a large tidal range plus a foot of sea level rise since 1920. Timing relative to high tide determines severity.

• Tropical systems

  Late August through September

  Infrequent but historically severe. Extratropical transition spreads damaging wind over a much wider area than the core.

• Heat waves

  June through August

  Humid heat in a city with old buildings and uneven air conditioning. Urban heat island effects are pronounced in dense neighborhoods.

• Severe thunderstorms

  June through August

  Damaging wind and hail. Tornadoes are rare but do occur in central and western Massachusetts.

What to wear and pack, by season

Spring (March to May)

Layers and a waterproof jacket. March is still winter here; May is genuinely pleasant.

Summer (June to August)

Warm-weather clothing, but bring a light layer for the sea breeze and for aggressively air-conditioned interiors.

Fall (September to November)

The best season. Light layers in September, a real jacket by early November.

Winter (December to February)

A serious coat, waterproof boots with grip, hat and gloves. Wind off the harbor makes the wind chill considerably worse than the air temperature suggests.