October through April is the season. Daytime temperatures hover between 18 and 28°C and the nights are cold enough for a jacket. In a wet winter, the wildflowers explode in late February or early March — locals will tell you whether it's a "super bloom" year or not, and the state park hotline updates daily.
Summer is brutal. From May through September daytime temperatures routinely top 40°C, hiking is dangerous from mid-morning onwards, and the town largely closes. The trade-off is solitude, the darkest skies of the year, and dirt-cheap lodging if you can stand the heat.