I don't know about where you guys live but right now in the valley it is hot with a capital "Holy crap it's hot". So to celebrate my sweatiness, we're going to learn how to give an image heat waves. You know, those magical rising thermals that come off the pavement, your car, and if you're not careful your head. Off we go...
Step 1: Pick an image that just looks hot. My image has the sun shining down on some railroad tracks.
Step 2: Crop the image how you want it, then get the image size. In Photoshop you can do this by selecting Image > Image size. Create a new Photoshop image with the same dimensions.
Step 3: With the new file open, paint the background black if it isn't already. Create a new layer.
Step 4: Now, select the area in this new, blank image that corresponds to where the heat waves should appear in your final picture. It might help to copy your picture (in our case, the train tracks) onto the new image to act as a template. Delete the layer when you're done.
You should end up with something like this (these images are not to scale - they're smaller than the train photo - yours should be the same size):
Step 5: Give your selection a feather by going to Select > Filter, and then fill it with white. I used a 50px feather to get this:
Step 6: Now here's where you can play a bit. With the faded, white layer selected, go to Filter > Distort > Ripple. I used a strength of 700%. You'll notice that the ripples are slanted a bit. Hit Ctrl + T to transform the layer, then pull, rotate and distort it as you please so that the ripples are more or less vertical. Hit Ctrl + F to reapply the ripple filter. You should have something like this:
Step 7: Apply a wave filter by going to Filter > Distort > Wave. Use the settings shown below, then hit Ctrl + F to apply it again.
Step 8: Save this image as a .psd file. Call it "Heat wave.psd".
Step 9: OK, back to the original image (the train tracks). With your image layer selected, go to Filter > Distort > Displace. Use a horizontal and vertical scale of 10, and leave the other options as is. Click "OK".
You'll be presented with a file browser, so pick the "Heat wave.psd" file you created a bit ago.
Step 10: You should have a pretty good heat wave going now, but to make it a little hotter looking, open your "Heat wave.psd" file and drag or copy the white, wavy layer to a new layer on your train tracks (or whatever) image. Give it a blend mode of "Overlay", set it at 30% opacity, and in layer styles, give it the default gradient (black on bottom fading to white on top) with a blend mode of "Soft Light". You should have something like this:
And there you go! I'm sweating just looking at this. Next time we'll do something colder.
More Tutorials: 
