CALTRANS Current Highway Information Search Current Road Conditions Enter Highway Number(s): Separate multiple route numbers with commas or spaces.

For Mammoth Mountain

Use 203 to know of road conditions up to the Mammoth Mountain ski area.
Ignore the section that may say.
SR 203
[IN THE CENTRAL CALIFORNIA AREA]
IS CLOSED FROM THE MAMMOTH MOUNTAIN INN (MONO CO) TO THE
MONO/MADERA CO LINE - FOR THE WINTER - MOTORISTS ARE ADVISED TO USE AN
ALTERNATE ROUTE

This is a normal winter condition pertaining to the road beyond the ski area.
Of course, if 203 is clear 395 is probably not having too many problems but you probably should check that also for good measure.

For June Mtn

Check conditions on SR 158 as well as 395. 3.5 MI NORTH OF JUNE LAKE VILLAGE is a normal winter closure point.