Booking with United Airlines 29 days in advance of your planned departure date is, on average, the best time to get cheap flights from San Francisco to Lisbon. The general trend is that the closer you book to the departure date, the more expensive your flight will be.
For Economy class flights, the cheapest month to fly this route is November. The most expensive months are June and July.
In terms of precipitation, rainfall in Lisbon ranges from 6.0 - 122.0 inches per month. December is typically the wettest month, when rainfall can reach 122.0 mm. July is typically the driest time to visit Lisbon when rainfall is around 6.0 mm.
If weather is an important factor for your trip to Lisbon, use this chart to help with planning. For those seeking warmer temperatures, July is the ideal time of year to visit, when temperatures reach an average of 23.0 C. Travellers hoping to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 11.0 C).
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