I have come across the following cool link showing the UV levels across the country, as the day develops. This map is quite handy in understanding whether the UV levels reported at ABIA and other local weather stations are a regional or national concern. Place your pointer over central Texas and watch the hourly map develop over the USA. Click here to see more from UV Awareness website.
For those of you interested in the NOAA Time series for UV (Dallas 1994-2012), click here. I hope to be doing some research on this during the summer.