Water damages can happen anywhere - AC units, water heaters, toilets, and kitchen sinks can go kablooey no matter where you live. Mold can also happen in any area where water intrudes into an artificial environment and is not immediately dried.
Mold is more prevalent in warmer, damper states (like our own lovely North and South Carolina) and as such may offer more overall opportunities; however, be aware that some states have started putting actual LAWS on the books regarding mold remediation, so it would behoove you to do some research to find out which states have regulation and whether your new company would be in compliance with those laws.
Warm, humid environments can also make mold more difficult to fight, since it is a natural phenomenon that exists in large quantities outside of buildings - it's hard to "clear" a mold job when spores are floating through the front door every time it's opened.
In short, temperature and humidity levels can give you more of a field to play in - but a good restoration company can succeed anywhere as long as they're aware of any laws in their area.