Well...unfortunately you can't have one without the other in USA...lol.
Possibly the most "even" temperatures year around would be Southern Florida, Southern Texas, Hawaii, Southern California; however, in those areas you have good chance of hurricanes.
States with least amounts of "natural disasters" would be those OUTSIDE of "Tornado Alley," hurricane prone coastal areas, completely avoiding California since it is another major earthquake waiting to happen. The Rocky Mountain region is obviously most prone to major snow storms as well as Western Oklahoma, Western Kansas and Nebraska...plus the other cold climate Northern areas.
Then there is Nevada... probably mostly desert... hasn't rained there and probably never will (joke, tongue-in-cheek)...
Let's not forget the Louisiana coastal areas (esp., New Orleans)...N.O. is obviously several feet below sea level and probably should have never been built...has flooded, will flood again, in spite of what government thinks and attempts to control... "Don't mess with Mother Nature"...lol.
Perhaps some other posters from other States can give their opinions from their areas and experiences...
I've lived in Texas, Colorado, Illinois, Missouri, Louisiana, South Dakota, and Kansas. Closest I've found to an "ideal" climate is our present location in Texas Panhandle region (we're in a "microclimate" spot next to Western Okla border) where most of "bad" weather around here splits to North and South when it heads here...including much needed rainfall.