It's been dry here too Brent, (up untill last Friday, that is). We went over 60 days without any rain and average temps in the upper 90's and low 100's.
With six inches of straw mulch around my trees though, I water twice a week...sometimes going 5 days between waterings. And these are all newly planted trees. Once the ground and the mulch get saturated, the area around the trees retains the moisture real well. (Having clay soil helps a lot too though). You won't see straw being used as mulch in Better Homes & Gardens, but it's cheap and it works.