I was searching around the Egypt.world file with S3PE for the .ini files (Resource Type 0x1f886ead) that control the sky and weather there and found 6 files. I extracted them and had a look at the contents and found that the file S3_1F886EAD_00000000_5E20253AF53E517F%%+_INI.ini contains the heat wave from Egypt and the contents of the SkyCommon.ini file found in The Sims 3\GameData\Shared\NonPackaged\Ini path.

I imported this file with S3PE into a world file I downloaded off the exchange, saved it and loaded up the game and the world has the heat wave effect!
The effect only affects the selected world and will not effect an unedited world (without this .ini file merged)


Update:
I have tested some worlds with the .ini file imported and all have worked correctly and have decided to do a simple tutorial bellow on how to do this yourself (you will need s3pe):

BEFORE YOU START REMEMBER TO backup YOUR WORLD FILE AND ANY SAVES FOR YOUR WORLD

REQUIRES WORLD ADVENTURES

1.Download and extract the attached .ini file to an easy to find folder.
2.Open S3PE and open your world you want to test this on.
3.Click on Resource -> import -> From file.
4.Navigate to the .ini file and open it. Click OK on the Resource Details window.
5.Click File -> Save and your world should have the heatwave effect.

Note: You can edit the ini file before importing and change the settings most values are easy to understand and have brief descriptions. But do not rename the file.

Note 2: This is not global, it will only affect the world you applied the .ini file to.

I wonder if it can be applied in CAW?

Another small thing I found about the heat wave effect, adding this line to Skycommon.ini under the [MiscSkyParams] part gives you the effect on all worlds:

;;Sets the Heat Shimmer Params
HeatShimmerDistance = 600

And configing the "HeatShimmerDistance = " changes the distance of the effect.

Updated to include a tutorial

This is excellent. I will definitely try to school myself so that I can try this out on my hot worlds! Thanks Ascarrott.

Me too! Thanks. Its perfect for my desert town.

Another thank you! This will work wonderfully on planned desert worlds!

Thanks for the Thanks!!

I have attached a pic from a downloaded world so you can see the heat wave in action.

The world is Oasis Island from here http://forum.thesims3.com/jforum/posts/list/148866.page

All I have done to it is edited the sun size and shimmer distance (heatwave) inside the .ini file and apply the .ini file to the world. Also I think I set the "HeatShimmerDistance =" value to 60 but it's a little close to the camera (Heatwave inside houses), so a value of 120 or more should be the minimum distance you set this to and to avoid a very wavy screen much like the fable drunk effect....

Edit: Sorry about small pics, this is due to max upload sizes.

...*ponders doing a neighborhood with about fifteen different nectariees, plus several academies of "Drunken Fighting" styles of Sim Fu and using the heatwave effect constantly*

If I add this to a world file used for a saved game, will it ruin the game save? Like, will the save not understand the file is the right one if I replace it with a new changed version?

If you want, Claeric, I can add that to my list of CAW things to test. The way Worlds are handled is tricky to me.

Thanks for the reply. I'm unsure so I'm just about to test this with a world I just downloaded, move some Sims in save after about 15 mins and load then save, then apply the .ini to it to see if it works.

Update:
Old saves are fine just make sure you don't rename the world file you are importing the .ini to and just to make sure, backup your saves and world before you start!

Will searching for "0x1f886ead" in a custom world find this so it can be edited? Or can I just replace it with no problems, automatically?

I got Kiki Tea's WA nua simoa and the wave effect is a bit too much for my eyes, it seems too close. I want to tone it down or remove it but I'm not sure how.

Yes it will open your the world file, put 0x1f886ead in the Resource type box, tick the tick boxes , then export it, edit it and import it. If you want to get rid of the heat wave effect delete the lines:
;;Sets the Heat Shimmer Params
HeatShimmerDistance = 400
Or if you want to change the distance change the number to a higher one (600 is what Egypt uses).