Fort Walton Beach, Florida – I’m all ready for a sweltering summer day on the Florida panhandle. On my checklist for this hot sunny day: parka, insulated pants, boots, toque, and thin, camera-friendly gloves that will be woefully inadequate at keeping my fingers warm.

Wait, what?

All of that is necessary to enter the main chamber at the McKinley Climatic Laboratory, which has been set to -28C so that Ford can winter-test its upcoming new vehicles.

(Disclaimer: Travel, accommodation and meals were provided to the author by the automaker.)

“When drivers get into the vehicle, they expect it to start right away and have a comfortable idle speed,” says Rich Shimon, Ford’s technical expert on gasoline powertrain calibration. “Our job is to make sure our vehicles do that under any conceivable condition and with any conceivable fuel, and now we’re doing the extreme cold-weather testing.”

The scene this day inside the chamber has been set up for the press. Three 2016 Super Duty models wear camouflage, since they have yet to be formally launched, and the F-150, Explorer, and Focus undergoing demonstration cold starts are current models. The remaining test vehicles, mostly 2017 and 2018 models, are hidden behind a curtain and will come back out once we leave.

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Ford has been using McKinley for the last decade, usually for three weeks each year, and has booked it for at least the next three years. While it has cold-weather chambers at its own test facility in Michigan, they’re much smaller and have to be shared with other departments. In McKinley’s largest chamber, Ford can bring in 72 vehicles and 54 engineers, all at once, for the entire three weeks. “It would take us months to get a week of testing (in Michigan),” Shimon says.

Size matters here. The McKinley Laboratory is part of the Eglin Air Force Base, and came about when the military discovered that many of the new airplanes that had been quickly designed and built for the Second World War wouldn’t start in cold weather. Test expert Lt. Col. Ashley McKinley knew that consistent, controlled conditions were vastly superior to taking equipment north and hoping for the right weather, and in 1943, work began on the facility.

It opened in 1947, and following a renovation that finished in 1997, it was made available for rent to private companies as well as military testing. It runs 24 hours a day, handling everything from tanks and tires, to Arctic survival gear and medical equipment. It’s so popular that if you want to book a short test window, your first opportunity is 2018. Want to stay for a longer test? Prepare to wait until 2020.

There are five operating chambers, but the one I’ve come to see is the eye-popping main one. It’s the world’s largest climatic chamber at 5,110 square metres (55,000 square feet), and can go as high as 78C, or as low as -65C. The facility can make rain, fog, snow, sand storms, ice storms and solar radiation, and can duplicate any type of weather except tornadoes and lightning strikes.

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Depending on the chamber you want and the weather you need, it costs between $8,000 and $30,000 (U.S.) per day to be here. In return, you get consistent conditions that are precisely accurate to whatever’s required, right down to the silica particle size in the sand storms.

Over the course of its three-week test, Ford started at -6C and will go to -40C, with most of the tests concentrating on how the vehicles start and idle in the cold. A wide variety of fuels are tested, representing different countries and regions, and engineers come from Ford centres around the globe. Shimon says the company calibrates common software that will work with everything, rather than tuning a car for one specific fuel in a sales region. That’s important because a vehicle that never leaves the area where it was sold might still have to cope with the different properties of winter and summer gasoline blends, or with varying amounts of ethanol.

The three Super Duty diesel models had been started up on the first day, and will idle 24/7 for the entire three weeks—just as some owners do in very harsh conditions, Shimon says. One of the tests will examine the diesel emissions catalysts to be sure that any residue burns off in the cold. If it doesn’t, it could degrade this expensive component.

The demonstration vehicles have been “cold-soaking” for hours, and the F-150 I climb into is as frozen as I am. It’s filled with test equipment, and a laptop starts recording data as the key is turned. Not only does the engine have to start right away, but it also has to idle smoothly, without revving up or slowing down. If the engineers discover an issue, they’ll try to fix it here and then forward the repair information back to head office. If they can’t figure it out, or if they run out of test time, they’ll take all the data back with them and use the smaller cold chambers in Michigan to iron it out.

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Ford uses the McKinley lab primarily for static testing. The floor’s too slippery to get the traction necessary to test transmissions and other components, and so drive testing waits for winter at a facility in Thompson, Manitoba. Meanwhile, shoehorning these cold-weather tests into the summer months helps to even out the development schedules of new vehicles. That’s all they do here: hot-weather testing is done at other sites.

For Shimon, it’s all about consistency, both in the chamber’s ambient temperature, and in calibrating the vehicles so they’ll react appropriately to it. “We have complex systems such as the injectors, throttle and actuators, and there’s not necessarily one right way of doing it,” he says. “We’re learning how to get the performance out of the engine, and across the environment and fuel economy too.”