Summers see very high daytime temperatures averaging mid-high 20s °C and often in the 30s °C. Wear a hat and sunscreen. Bring 2 to 3 litres of water/person/day, drinking water is available at the Frenchman Valley Campground. Rapidly changing weather conditions are common, especially late afternoon thunder and lightning in summer. Severe winds are dangerous, and finding shelter can be difficult. Evenings cool down into the high teens-low 20s °C. Little rain falls in the area of the park - usually in the form of short-lived showers. But when it does arrive in any quantity, park roads become impassable when wet.
Having the essential items in your pack, filing a trip plan, checking current weather forecasts and making sure your gear is in good condition before heading out can keep a minor issue from becoming an emergency.