Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Montana to Petersburg, Alaska as you normally would.
In terms of precipitation, rainfall in Petersburg, Alaska ranges from 5.1 - 16.3 inches per month. October is typically the wettest month, when rainfall can reach 16.3 in. June is typically the driest time to visit Petersburg, Alaska when rainfall is around 5.1 in.
If weather is an important factor for your trip to Petersburg, Alaska, 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 55.4 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 26.6 F).