Hot and humid vs. hot and dry

Today promises to be a typical hot, humid Carolina low-lands' day.  Back home the upper mid-west is sweltering, but the big difference is that here it's humid and there it's dry.  In out particular area summer always brings hot days, but there have been summers when we've barely turned on the AC.  But when you string together day after day of 90s and even the occasional 100 degree high, our weather is more like what you expect in Tulsa, and who wants to live in Tulsa?  Unless some thunderstorm activity intervenes and waters our gardens, we expect to find some losses among the newly planted.  One of the problems of doing everything ourselves, no one else knows when and where things are planted, and therefore a house-cat sitter has no idea what to do if you say "water the new Japanese yews".  Actually the needs-water list is rather long this year, and just watering the potted/house plants is quite a chore, so our vacation may end up costing us more than we planned.  Maybe we need to start a coop garden babysitting service because having someone who knows gardens and plants would make things much easier.  Anybody part of such a thing?