Hi donbrowne,
There is more about the pros and cons of memory foam in this article and one of the “cons” for some (but certainly not all) people is that it can sleep warmer than other foam materials.
There is also more in post #2 here about the many variables that combine together to affect the sleeping temperature of a mattress besides just the type of foam layers in the mattress. While memory foam tends to sleep warmer than other types of foam materials (such as polyfoam or latex) for most people … there are many different types of memory foam that are more or less breathable and there are also other factors such as the mattress cover, any quilting layers, your mattress protector, your sheets and bedding, and your bedclothes that can have a significant effect on sleeping temperature as well.
There is also more about some of the different ways that manufacturers use to “cool down” memory foam in post #6 here.
I would also make sure you read the mattress shopping tutorial here which has all the basic information, steps, and guidelines that you will need to make the best possible choices … and know how and why to avoid the worst ones. There are many mattresses that don’t use memory foam in their design (there are more that don’t than do). The “coolest” mattress of all would be an innerspring with natural fibers that didn’t use any foam at all but these can be much more costly and are often firmer than mattresses that use foams. Some of these are listed in post #4 here.
Once you are at step 3 in the tutorial and you are ready to start testing mattresses then the better options and possibilities I’m aware of in the Houston area are listed in post #2 here.
Phoenix