The high temperatures of summer can cause heat exhaustion or even heat stroke. Avoid strenuous activities during the day. Drink plenty of water, even when you are not thirsty; your body can lose large amounts of water without you realizing it.
Wildlife: Rattlesnakes, one type of scorpion, and the Gila monster are poisonous, but will leave you alone unless disturbed or cornered. Wear sturdy boots and watch where you step.
Amoeba: A microscopic amoeba, Naegleria fowleri, which can live in hot springs, can cause a rare infection and sometimes death. Do not dive or submerse your head in warm springs or associated streams.
Plants: Oleander is a toxic plant common to developed areas; neither you nor your pet should eat any plant part or drink water from ditches near the oleander.
Lightning and Flash Floods
Desert thunderstorms carry the double threat of flash floods and lightning. They occur most often in summer and fall. Be wary of nearby storms. Violent downpours can cause flash flooding in distant areas untouched by rain. Never camp in a wash or other low-lying area or drive across a flooded road. Stay out of open areas where lightning may strike. Weather information is posted daily at ranger stations.
Mines and Tunnels
Abandoned mines and tunnels, with their deep shafts and old, rotten supporting timbers, are dangerous. Stay away from them!