Overview: San Bernardino, CASan Bernardino, CA (United States of America) is a place with a tropical climate. Temperatures during the day are in the range from 19 °C (67 °F) in December to 35 °C (96 °F) in August. The highest night temperatures could be experienced in August with 17 °C (63 °F), the lowest in December with 5 °C (42 °F). The least rainy month in San Bernardino, CA is June with its 1 day of rain, the rainiest month is February, when it rains 6 days.