Overview: Mount Rainier National ParkMount Rainier National Park (United States of America) is a place with a cold climate. Temperatures during the day are in the range from -4 °C (25 °F) in December to 17 °C (62 °F) in August. The highest night temperatures could be experienced in August with 8 °C (46 °F), the lowest in December with -11 °C (13 °F). The least rainy month in Mount Rainier National Park is August with its 6 days of rain, the rainiest month is November, when it rains 19 days.