Why is the average annual high temperature in Cape Hatteras,
NC higher than the average annual temperature in Monterey. CA

There is less variation in the seasonal temperatures on the West Coast than on the East Coast.  

Explanation:

The weather of the West Coast is influenced by 2 major geographical features – the Pacific Ocean and the mountain ranges along the coast. These two work in unison to create the weather patterns that characterize the West Coast.  There is less variation in temperatures on the West Coast than there is in the East. Cape Hatteras gets very hot in the months of July and August, whereas in Monterey, CA the average annual high is 63.5°F and the temperature variation between Summer and Winter is only roughly 8 to 10 degrees Fahrenheit.  In Cape Hatteras the average annual high is 68.8°F. There is a 30 degree difference between the average highs in January and July in Cape Hatteras according to U.S Climate Data.