Like much of California, the Petaluma area is fortunate in that it enjoys a mild Mediterranean climate year-round, but it is also home to numerous micro-climates. The environmental factors that determine the local climate are proximity to the ocean, the elevation, and the presence of hills and mountains to the east and west. Coastal California’s prevailing weather systems tend to come from the Pacific Ocean. Places closer to the ocean and on the windward side of mountains tend to receive more rain from autumn through spring and more summer wind and fog. Areas further inland and in the lee of significant elevations tend to receive less rain and less, in some cases no, fog in the summer. The Petaluma area and the Santa Rosa Plain are also prone to this normal fog pattern, though they tend to receive the fog later in the evening and mid-day temperatures are significantly higher than they are on the coast.

High temperatures in the Petaluma are range from the 50s and 60s in the winter months to the 70s and 80s in the summer months, and low temperatures range from the high 30s to 60s. The driest months in the Petaluma area are July and August, with November and January typically being the wettest months. Sonoma County sees an average yearly precipitation of about 29 inches.

Snow is very rare in Sonoma County except in the higher elevations on and around the Mayacamas Mountains.

With its mild temperatures year-round, Petaluma is a wonderful destination during any season. If you like the hustle-and-bustle of a small town during high season, plan to visit during the summer and fall. If you enjoy a more relaxed, low-key environment, plan to come during the winter and early spring months. Petaluma is a beautiful place to visit all year long.