For me it's more about the dew point and the predicted high. If the dew points are upper 60s/ low 70s the air conditioning will come on with a high of 85. If the dew points are okay I'll usually be okay to a high of 90. It's rare when the AC stays on for several days in a row. (Of course, here in MN the cooling season is only about 2 months long, so we don't have to worry quite as much as those of you in Texas
)