I have stated before that it would take two major events to break down the persistent Sonoran heat ridge that has been frying the southwestern and south central USA. A cold front and major hurricane working in combination could do it. But I might also add the influence of El Nino, with the return of an active southern branch jet stream. All model guidance shows a cold frontal passage in the middle of next week that should clear the Rio Grande and the Gulf Coast. Of course that means about five or six days of difficulty for Texas with regard to heat. But the arrival of the boundary will also mean lifting and forcing (with a highly unstable atmosphere to work with). I favor the operational ECMWF model scenario, which would allow for multiple thunderstorm cases in dry Texas and Appalachia and the Eastern Seaboard over the next week to ten days.
Of Hurricane Lee grows as strong as models project, and takes a track well off the East Coast but making a quick landfall in Nova Scotia, and extra incentive for deepening the 500MB trough will mean a cooler response east of the Rocky Mountains that should last through about September 22. In addition, the influence of the El Nino episode should aid in the strengthening of the southern branch jet stream, with a shortwave coming into California in the 11-15 day period, ending the heat in the Southwest. This impulse could draw up from the huge moisture array associated with major hurricane Jova, now moving west/northwest away from Mexico (but inundating the Mexican Riviera with convection).