Average annual precipitation in this area is 38 inches, with June receiving the most precipitation and February receiving the least. Harpers Ferry's average annual high temperature is 63 degrees F, with July being the hottest month. The average annual low temperature here is 40 degrees F, with January being the coldest month. The average high in the summer is 82 degrees F, whereas the average low in the winter is 27 degrees F. The temperature here reaches 90 degrees F or higher at least 30 days each year and humidity can be oppressive when maritime air penetrates inland from coastal areas. Once every 25 years an extreme annual low of -11 degrees F is expected.