Cumulus Crowned Mountains

Cumulus clouds billow above the San Bernardino Mountains in this view looking northwest from Dillon Road in Desert Hot Springs, California around 2:32 PM PDT, Sunday, September 8, 2013. The mountains are about 20 miles away. Mountain can be a boundary between air masses of different temperature, pressure changes, and wind directions. The boundary is where they mix, and the changes create these cloud formations. Air temperature here was around 100 degrees F.