Mac:

… The Pacific Crest Trail Association, the Continental Divide Trail Coalition, and the Appalachian Trail Conservancy have all officially requested hikers to postpone or cancel their thru-hikes

… (in related news, the Arizona Trail Association and the Great Divide Trail Association have done the same). …

Your Pacific Crest Trail Thru-hike Is Canceled

You can certainly still day hike. And should be able to plan multi-day hikes.

BUT check camping and resupply options. California State Parks, for example, has closed all campgrounds.