The weather looked neither hot nor cold the entire movie!

They used special cameras that do not show unpleasant weather.

And in the parts the movie was set, humid too. Austin and San Marcos -- humid, Houston, super humid.

I'm thinking they must have have been shooting in that nice little window in late fall when the heat and humidity have gone downward but it's not yet chilly weather that needs a jacket or sweater. Or even late winter just before the spring mugginess comes.

The indoor scenes of course could be shot anytime with plenty of air conditioning.