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Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Indianapolis to Portimão as you normally would.
In terms of precipitation, rainfall in Portimão ranges from 0.1 - 4.6 inches per month. December is typically the wettest month, when rainfall can reach 4.6 in. July is typically the driest time to visit Portimão when rainfall is around 0.1 in.
If weather is an important factor for your trip to Portimão, 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 75.2 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 53.6 F).