"Heat haze" refers to the wavy appearance or shimmering effect you see above the ground on a hot day. It happens because the air near the surface gets heated by the sun, causing the light to bend and create a distorted image. Full definition
Mine billowed like the kind of heat haze that you get in Guyana in the middle of the day. (painters-table.com)
Blue Heat Haze (the main theme of The Legend of Dark Witch, «Aoi Kagero» in Japanese. (perfectly-nintendo.com)
I ought to be able to see 3 miles to the horizon, but there's a solid heat haze in front of me, so it looks like I'm constantly approaching a crest. (automobilemag.com)