Castle Crags State Park
Northern California's Castle Crags State Park has lots of low-elevation, south-facing acreage, making it a great all-year hiking spot. With few exceptions I've been able to hike there in every month of the year. Adjacent to the park is the Castella, CA Post Office (96017), and food and gas are available (not necessarily in that order) at Ammirati's Market at the freeway offramp. The closest ATM is almost 5 miles north at Manfredi's on the south end of Dunsmuir.
This site shows established trails in the Park itself as well as hiking possibilities in the adjoining Wilderness Area, and you can download a map of campground area trails, as well as a larger scale map showing more trails in the Park itself.
There is also a section in the archives with information on hikes I took in and around the Park from 2014 to 2017.
A page from the National Weather Service with local weather info is available online.
If you're wondering about road conditions, CalTrans has a page with a webcam showing the freeway on the north end of Dunsmuir, about 6 miles north of the Park entrance, and another page showing all of the webcams in the northern end of the state.