Updated 5:07 p.m. Katy ISD announced its campuses will remain closed Wednesday due to "extremely cold and freezing temperatures anticipated to impact roads and driving conditions." Published 10:54 a.m. Houston Transtar showed ice on the Grand Parkway at its intersection with I-10 in Katy around 10:15 a.m. Tuesday, while ice had also accumulated on I-10 at Pin Oak Road. A winter storm warning is in effect for the Greater Houston area as a wintry precipitation mix is expected to precede temperatures in the teens and 20s overnight, according to the National Weather Service. Transtar cameras showed highway traffic was moving normally by 10:30 a.m., except on the Grand Parkway between I-10 and Westpark Tollway/FM 1093, where cars were moving between 50 percent and 120 percent slower than usual. Meanwhile, Katy ISD closed campuses for the day and city of Katy offices were also shuttered, with trash services for Franz Road cancelled for the day.   Drivers are being encouraged by county and public safety offices to stay off roads unless necessary. Some around Katy took to social media to post pictures of their iced over vehicles and homes.