Kelly Norton compiled NOAA data for the last 23 years to figure out the regions of the United States with the most (and least) pleasant days in a typical year.
He defines “pleasant” as having a mean temperature between (55°F and 75°F or 13/24C), a minimum temperature above 45° F (7C), a maximum temperature below 85° F (29C) and no significant precipitation or snow depth.
He put it all in an interactive map (he's a software engineer) where you can click to explore your area's degree of "pleasantness."
Example (the bluer, the better):
By this measure, Los Angeles has the most pleasant weather in the US; McAllister, MT, the least.