You are sure to experience warm daytime weather in June and pleasantly cool nights in the Napa Valley.
The average June temperature in Calistoga is 68 degrees, with an average high of 86, and an average low of 50 degrees. The average rainfall in Calistoga for June is 0.22 inches. In the town of Napa, the average temperature in June is 66 degrees, while the average high is 78 and the average low temperature is 51. The average rainfall for June is 0.3 inches.
In 2014, June saw some very hot days, with temperatures hitting 90 on seven days, and one day, reaching 100. What is really nice about hot weather in June is that the temperature invariably cools down at night, and on the day the temperature hit 100 as a high, it cooled to 53 that night. In short, June has great weather and is a fantastic month to visit Napa Valley.