Until relative humidity hits 100% at 80F and you hate your life (and your house due to the condensing moisture). Air conditioning is in large part about humidity control which using the ground will actually increase as best I can tell.

You know nothing about Houston if you think we can go "down" at all without digging a swimming pool.

Humidity is as much the enemy here as heat. AC is how we mitigate that.

Not sure how far down you can go in Houston before you're under water. Downtown is only 15m above sea level apparently.

https://en.wikipedia.org/wiki/Geography_of_Houston