The ideal weather for whitewashing
The slower the lime hardens, the more durable it'll get. Therefore, the best time for whitewashing is when there is a high humidity and the temperature is not too high. Thus, the ideal weather for whitewashing is an overcast day with temperatures between 5 - 20 degrees, so a typical time to whitewash is either in spring or autumn. However, it is possible to whitewash on a sunny summer day but then you have to make sure only to whitewash the shady side of the house after the sun has been on this side. Lime should not be exposed to frost and can't harden adequately below 5 degrees, which makes it almost impossible to whitewash during the winter.