the car won't start all dash lights are on and the battery is fully charged

Does it still crank, but not start? Can you hear the fuel pump turn on for a couple seconds when you try and start the vehicle? Maybe the heat is affecting older parts. More information is needed, and an experienced technician should diagnose your vehicle. There are a lot of variables here.

you have some kind of control problem with either the ignition swictch or wiring. you need a shop to check it out and give you a bid. Roy