August is the cheapest month to fly this route, with average fares around $853 round trip.
Average round-trip fares by departure month, based on current availability.
| Month | Avg Price | Lowest | Relative Cost | |
|---|---|---|---|---|
| May 2026 | $965 | $822 | ||
| June 2026 | $1019 | $890 | Peak | |
| July 2026 | $904 | $879 | ||
| August 2026 | $853 | $836 | Best |
Departing on Tuesday offers the lowest average fares at $928. Thursday departures are the most expensive at $1000, a difference of $72.
The best time to fly is August. Set up an alert and we'll notify you when prices drop.
Get Started Free →The cheapest month to fly from Seattle to London is August, with average round-trip fares around $853. The lowest fare found in August is $836.
Tuesday departures are the cheapest, averaging $928 round trip. The most expensive day is Thursday at $1000.
Based on current pricing trends, booking for August travel offers the best value. Avoid June if possible, as fares average $1019 compared to $853 in the cheapest month. May is a solid middle-ground option at $965.
Flying in August instead of June can save you approximately $166 per round trip. The cheapest month averages $853 while the most expensive averages $1019.
Airlines, flight times, price calendar, and more for Seattle to London
View SEA → LHR Details