Depends on the variety you planted -- there are several that can stand Texas
heat and since you planted in a pot you can always move it to a place where
it gets some shade. If it is an indeterminate and you keep it cared for it
may slow down during the really bad heat but recover and start producing
again when it gets a bit cooler.

Ideally you should start tomatoes here a bit early -- like in February or
March then baby them and protect them from the occasional freeze we will
still have here until April but if you wait until April you have missed a
lot of growing time before the hard months hit.

Last year it got so hot I had tomatoes that seemed to cook on the vine --
but a neighbor's did ok through the heat -- so partly it is variety and
partly if when it gets terribly hot that you can offer the plants some
shade.

My mom lives in Sun City up in Georgetown and has successfully grown
tomatoes every year throughout the summer by having them in pots -- just
have to wait and see! Good luck!

--
Marta
(if you email me directly you need to remove the X )