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In terms of precipitation, rainfall in Londonderry ranges from 2.2 - 4.7 inches per month. October is typically the wettest month, when rainfall can reach 4.7 in. April is typically the driest time to visit Londonderry when rainfall is around 2.2 in.
If weather is an important factor for your trip to Londonderry, 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 57.2 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 42.8 F).