Over 3.7 million vehicles on American roads have been slapped with a "park outside" recall, a number that has shot up by 40 percent since May last year, and owners are getting an urgent nudge to heed warnings following data from CARFAX. Among the swelling ranks of these potentially flammable cars, Houston takes an unwelcome spot in the top 10 cities, now hosting upwards of 330,000 vehicles affected by this recall, FOX 26 Houston reports.

Metro areas are seeing numbers nearly doubling, as Atlanta's count surged to 113,000 in January from about 64,000 vehicles last May. California's figures are even more jarring, with 368,000 cars across the state tagged with the recall, and Los Angeles alone accounting for nearly half of that total—a nearly fourfold leap from May's numbers of 93,000, according to Fox Business. This increasing trend encompasses vehicles awaiting repair and those whose owners have yet to bring them in for service.

The concern has become particularly acute for owners of certain models from Hyundai and Kia. The two automakers, flagged by the U.S. Department of Transportation, have seen over 3,100 vehicles go up in flames across the nation. Models from Lincoln and certain Jeep Cherokees from Chrysler have not been spared either, both issuing recalls due to fire risks and urging owners to park their cars away from structures— even if the vehicles are turned off, as they too can spontaneously combust.

"The biggest issue right now with the recall is that these very small issues, like a fuel leak, can lead to a short," CARFAX spokesperson Mike Lavigne lamented, as told to FOX 26 Houston. "A short can lead to a fire and this can happen, the scary part, when the vehicle isn't even in operation at all. It can be sitting outside your house, cold and off, and still be at risk of a fire."

For car owners unsure about their vehicle's status, the process to check is straightforward: locate the VIN at the bottom corner of the windshield, visit Carfax.com/recall, and input the number to quickly discern if your vehicle is on the recall list. The urgency conveyed by experts is clear: act fast to prevent potential disaster without any human interaction or outside interference as "something could happen with no outside interference or any human interaction," as Lavigne explained in a sobering note from Fox Business.