It is no surprise that it is hot in Houston during the summer, however it has been especially so recently. Violin family instruments are especially sensitive to the heat for a couple of reasons:
1. the glue which holds the instrument together is water/heat soluble. I have literally seen necks pop out of violins when they were left in a hot car.
2. the varnish is also heat sensitive. An instrument left in a hot trunk on the way home from shopping can literally bubble and cook on the instrument. This type of damage is expensive to fix and in some cases, it cannot be, without stripping the instrument.
The easiest tip I can provide is to keep your instrument cool and comfortable like you would a pet or a child. If they are uncomfortable, so is your instrument! Ideal temperatures would be room temperature (69-75 degrees) with a humidity between 40-60%.