Very hot. The City of Peoria says artificial turf surface temperatures can reach the same temperature as asphalt or higher, and cites Scottsdale research that measured turf at 180°F, 40°F hotter than nearby asphalt. Turf can still work in a Peoria yard, but only if you plan where it goes and when people use it.
What the official sources say
The City of Peoria's artificial turf page summarizes the research: surface temperatures can reach or pass asphalt, turf provides no natural cooling, and it suits small, shaded areas best. AMWUA, the association of Phoenix-area municipal water providers, adds that turf will never be as cool to the touch as real grass and can become too hot for children and pets to play on.
Those are surface temperatures in direct sun. Air temperature, shade, time of day and the turf product all change what you feel underfoot.
Shade makes the biggest difference
The most reliable way to keep turf usable is to keep the sun off it. In practice that means placing turf where the house, a patio cover, a shade sail or trees cover it in the afternoon, and using gravel or desert plants for the hottest exposure.
In Peoria, west and south-facing backyards take the hardest afternoon sun. If that's your only open space, consider a smaller turf area under shade instead of turfing the whole yard.
Cooling and "cool" products
Spraying turf with water cools it for a short time, which is why some installs include a sprinkler for cooling. The city notes that cooling and cleaning water may limit the overall water savings.
Some products and infills are sold as running cooler. Ask what testing supports the claim and expect a modest difference, not grass-like temperatures in full sun.
Kids and pets
Check the surface with the back of your hand before kids or pets go out on a summer afternoon. Plan play areas and dog runs where they'll be shaded, and see our pet turf page for setting up a dog area that stays more comfortable.
When turf isn't the right answer
For a big, unshaded yard, desert plants and trees may serve you better. Our comparison of turf, xeriscape and grass walks through the options, including the city rebate for desert plants.