August is the best month to visit Mammoth Lakes. There are only 4 days of rain in the whole month, so you can leave your umbrella at home. There are some people, who may feel a slight chill at 23.2 °C (73.8 °F), but others will feel perfectly fine. The temperature of 8.5 °C (47.3 °F) at night may make it better to dine inside or to put on more clothes for a dinner outside.