"It's called 'black ice' because it tends to look like the rest of the pavement on the road, although in reality, it's actually clear," the US Forest Service notes. "Black ice forms without creating bubbles, which allows it to blend in with any surface it forms over. Black ice is dangerous precisely because it's hard to detect."

With freezing temperatures holding firm, much of Houston remains at a standstill, as schools, businesses and many roads remained closed Wednesday morning. State of play: Driving on roads is still not advised as melted snow has refrozen.

A historic winter storm swept across the Gulf Coast on Tuesday, bringing heavy snow and icy conditions to the Southeast while most of the country was facing dangerously cold temperatures from an arctic blast that arrived over the weekend.

Highs on Thursday have a good chance of hitting the low 50s with lots of sunshine. That should help to melt any remaining snow or ice across the Houston area.

Tuesday's snow largely melted Wednesday as temperatures climbed from the teens into the 40s. Highs in the lows 50s are forecasted for Thursday and Friday, with temperatures reaching the 60s this weekend,