Anglers over 16 must have a fishing license. Summers at Sugarloaf Ridge are hot and dry. High temperatures are often in the 90s, but it usually cools down in the evening to the 40s. Ocean fog sometimes penetrates this far inland. Most of the park's forty inches or so of rain come between November and April.
Light snow falls occasionally.
Wintertime low temperatures drop into the 30s with daytime highs in the 50s and 60's. People find this area most enjoyable during the spring and fall. After the winter rains, there is a picturesque 25-foot waterfall along Sonoma Creek below the campground. Also in the spring, the park comes alive with wildflowers including California poppies, cream cups, lupine, penstemon, buttercups, several varieties of pea, shooting stars, trillium, and Indian warrior. Less common are golden fairy lantern, zigadene, and fritillaria.