Really???

So, yesterday we were driving across Houston to Caleb's favorite cousin, JR's, fifth birthday party. Somewhere along the Katy freeway, I noticed one of those yellow signs...

Are they for real? And wouldn't you know it...I saw the same signs on the next two "bridges" (or overpasses...whatever). Doesn't the highway department know that it's a hundred-freakin-degrees already??? As my dad put it, was there an ice truck overturned or something???