Texas Rain

Residents new to San Antonio often remark how local drivers don't know how to drive in the rain. I suppose perpetual drought may have something to do with it. However, when the city of San Antonio posts a sign like this on the interstate while its raining:

one readily suspects that the locals really don't know how to drive in the rain.

More seriously, however this part of the state can experience flash floods because the land here saturates quickly. In that case, police make every effort to prevent people from entering low water crossings where a car (or person!) can be swept away.

But I lean towards the lack of ability theory...

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Update:

The sign was later altered to say "When flooded, turn around, don't drown." Well, now that makes sense!

http://www.nws.noaa.gov/os/water/tadd/