Depending on how realistic and detailed you need to get, I quickly played with the “Sony Wave” VFX, which I applied to a test video clip. As a starting place, every 5 seconds I put down a keyframe. All the odd (1st, 3rd, 5th, etc.) keyframes had all Wave controls set to 0.0. Every even (2nd, 4th, 6th, etc.) keyframe I set the Horizontal Waves = 10.0 and the Horizontal Amplitude to 0.003. All keyframes were set to the Smooth Fade transition type (right-click the keyframe for context menu). I then added a second “Sony Wave” VFX to the same clip and keyframed it exactly the same, except for this, I changed the Vertical rather than the Horizontal values. I think this could be tweaked a bit more to get a usable simulation of the heat wave you want.