There is not only one single place to find this information on the Internet.

Basically the farther south you go, the less the changes in barometric pressure; the Southwest US probably has the least variation. The problem with Florida would be hurricanes and tropical storms from June to November.

You can also look at:
http://ols.nndc.noaa.gov/plolstore/plsql/olstore.prodspecific?prodnum=C00095-PUB-A0001#TABLES
http://hurricane.ncdc.noaa.gov/cgi-bin/climatenormals/climatenormals.pl