There are
1,208 mi
from Longmont, CO to Clearlake, CA
That's the driving distance. It would take 21 hours 10 mins to go from Longmont, Colorado to Clearlake, California.
The flight distance (direct flight from Longmont, CO to Clearlake, CA) is 935.63 mi.
1,208 mi = 1.61 kms