Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from District of Columbia to Pasto as you normally would.
In terms of precipitation, rainfall in Pasto ranges from 1.2 - 3.7 inches per month. November is typically the wettest month, when rainfall can reach 3.7 in. August is typically the driest time to visit Pasto when rainfall is around 1.2 in.
If weather is an important factor for your trip to Pasto, use this chart to help with planning. For those seeking warmer temperatures, April is the ideal time of year to visit, when temperatures reach an average of 57.2 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 55.4 F).