You do not need electrolyte replacement which is something put out by the Gatorade marketing department. The company pays the NFL teams to use their product and advertise it on the sidelines.
If your core temperature is over 103 degrees it needs to get in a cooler environment to recover. What is essential is staying hydrated to keep your blood as thin as possible and minimize the stress on your heart. Heat stroke victims have core temperatures of more than 105 degrees and then go into cardiac arrest as their hearts cannot cope.
In Phoenix the temperature of the asphalt gets up to 170 degrees. That heat is reflected back up to anyone one it whether they are walking or bicycling. Qutite a few people getting admitted to the ER with third degree burns on their feet when they have been stupid enough to go outside barefoot.
Buy a cheap thermometer and use it to check your body temperature. Nothing high tech or expensive is needed to determine your current state. And wear a long sleeved shirt and a hat and try to stay out of the sun and off the pavement.
Glad to hear you are letting your cats outside in the heat. Two many free roaming cats as it is and a few less is good for the local wildlife.