In terms of precipitation, rainfall in Portsmouth ranges from 1.0 - 3.0 inches per month. December is typically the wettest month, when rainfall can reach 3.0 in. July is typically the driest time to visit Portsmouth when rainfall is around 1.0 in.
If weather is an important factor for your trip to Portsmouth, 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 64.4 F. Travelers looking to avoid the cold should look outside of December, when temperatures are typically at their lowest (around 39.2 F).