Per the Dallas Morning News, today's Rangers/Mariners game has been postponed due to bad weather. There's no word on a makeup date yet.
As of this writing at 1:45 PM, Denton and Tarrant (which houses Arlington) counties are under severe thunderstorm warnings, and the western half of the Metroplex is under a tornado watch until 8:00 PM CST. Things are expected to get much worse over the rest of the day weather wise.
UPDATE: Today's game has been rescheduled as part of a doubleheader when the Mariners come back to town July 23-25. Texas is using the rainout to skip Brandon McCarthy in the rotation; he will start on Sunday. Vicente Padilla will start tomorrow against the Cleveland Indians, followed by Kameron Loe on Thursday, Robinson Tejeda on Friday and Kevin Millwood on Saturday.
There are confirmed tornado touchdowns in the Metroplex area. The first wave of storms appears to have passed through, but there's more trouble on the way - and not just for DFW. Northeast and central Texas have been upgraded to a "high risk" area by the Storm Prediction Center; it's looking like a rough few hours ahead.