May in the Napa Valley gives visitors a taste of summer and spring all at once with some days of very warm daytime temperatures and some fairly chilly nights.
The average May temperature in Calistoga is 64 degrees, with an average high of 78, and an average low of 46 degrees. The average rainfall in Calistoga for May is 1.4 inches.
Although it is still technically spring, May in Napa Valley often feels like summer. In May 2014, for example, high temperatures were generally in the 70’s and 80’s with the temperature exceeding 90 on five days. Rainfall is practically non-existent in May, with average monthly rainfall of just a half inch. There is hardly a cloud and the sun shines 11 hours a day.