Today the President of The United States is coming to Houston for a rally. He is promoting Ted Cruz in the 2018 mid-term elections here in Texas. You will not be able to fly anywhere near Houston today starting at 1615 (4:15pm) to 2030 (8:30pm).
TFR (Temporary Flight Restrictions) from the FAA. https://tfr.faa.gov/save_pages/detail_8_7373.html