What's the cheapest day to fly in September?

We don't have enough real fare data for September to identify a cheapest weekday.

Is September a good time to visit Seattle?

Check the real weather data above for Seattle in September — we don't have crowd or event data to add beyond that.

Should I book now or wait?

There's no reliable way to predict whether a specific fare will rise or fall. If the real September fares above already fit your budget, booking removes the risk of the price changing.

Search Boston → Seattle in September

Compare flights, hotels, cars, and activities for this trip in one place.

Direct flights onlyMy dates are flexible (±3 days)Don't know where yet? Explore everywhere

500+airlines & travel sites compared

1,200+routes tracked

€0booking fees from us

Flights from Boston to Seattle in September

Planning a trip from Boston to Seattle in September? Find the best flights and seasonal tips. Flight time: 5h 25m.

Flying in September

Seattle typically sees daytime highs around 22°C and overnight lows around 12°C in September, based on the last 3 years. Expect roughly 61 mm of rain across the month.