2001 Ford F-150 Shuts off while driving in hot humid weather

My 2001 F-150 has started stalling, while driving but only on days when it's 90 degrees plus. It's happened with and without the A/C being on but on all occasions the A/C had been on at some point during the trip. Yesterday it started up and ran for about 30 minutes and then on a interstate off ramp just died (at about 50 mph). It will then not restart. It will crank but it's almost like it's getting no fuel. No fuel smell when attempting restarts. The truck will start like a champ after it sits about 30-40 minutes. After that it will run, but I am not sure for how long - I haven't been brave enough to push it.