WATER. It's VITAL. Take a bottle with you all summer long. Dehydration is very damaging, as well as overheating. Get freezer baggies and half-fill them with water, freeze them, and if you start feeling wonky, nauseated, or disoriented from working in the heat, get a thin towel and wrap the frozen baggie of ice and APPLY AROUND YOUR NECK or under your armpits. Blood expels excess heat from the body, and those (and the groin) are where major vessels are closest to the skin. A 95 F / 35 C report means "in the shade" -- if you are in the sun, there's no telling how hot it is, especially if humidity is high with little wind (i.e. your sweat does not cool you effectively)! Remember, a 105 F / 41 C body temperature from illness can kill you, so STAY COOL and don't fry your brain with overwork in the heat.
And if you see someone get wobbly or disoriented, or even collapse in the heat, splash any cool liquid you can around their neck or hair, even if you have to dump your icy soft drink on them. If it works to rouse them, you may not need to call an ambulance; if it doesn't, they may have other things wrong, too. KEEP WATER HANDY!