The summer heat has fully set in, and the region is preparing for a brutal heat wave in the coming days. And Metro isn't making the situation any better with its latest major problem: #hotcars.

Yes, it's actually a trending hashtag on Twitter for the area, and while it's not actually a new problem, it's getting renewed attention with the summer heat. What does it refer to? A recurring HVAC problem that is causing air conditioning to shut off in many of its rail cars, leaving riders sweltering in 90-degree-plus temperatures while crammed in with many other sweaty riders.

It's actually Metro's brand new rail cars, the 7000-series, that are at the heart of the problem. WAMU reported Monday that a WMATA official said a software patch should fix the problem by the end of the week — so sadly, even in a best-case scenario, riders will be enduring hell on Earth this work week.