Please check these road conditions right before your departure to Mammoth!
Current Road Conditions as reported every 15 minutes by CalTrans (click on the links below)
US Highway 395 (Main Highway to Mammoth)
State Route 203 (Also known as Main Street in Mammoth)
State Route 14
US Highway 50
Or you can call Caltrans. This is a great automated system reporting current road conditions!