Waymo announced on Thursday that it is bringing its Chrysler Pacifica minivans to the Detroit area to test how the company's technology performs in the region's harsh winters.

"Our ultimate goal is for our fully self-driving cars to operate safely and smoothly in all kinds of environments," Waymo CEO John Krafcik writes.

Krafcik says that Waymo has been doing cold-weather tests since 2012. But so far Waymo has done most of its testing in sunny places like Mountain View, California; Phoenix, Arizona; and Austin, Texas. where snow is rare. Waymo believes it has largely mastered driving in sunny climates and is preparing to launch a commercial service in the sun-drenched Phoenix area.

Ultimately, though, Waymo is going to want to offer service in snowy cities like Minneapolis, Chicago, and Boston.

"This type of testing will give us the opportunity to assess the way our sensors perform in wet, cold conditions," Krafick writes. "And it will also build on the advanced driving skills we’ve developed over the last eight years by teaching our cars how to handle things like skidding on icy, unplowed roads."

Detroit is an obvious choice for cold-weather testing. The city is home to the America's major automakers, and Waymo already has a facility there for collaborating with car companies. And the Michigan legislature passed a bill last year to encourage more testing of self-driving vehicles in the state.

Waymo's approach here illustrates one of the big advantages of the company's taxi-oriented business strategy. If Waymo wanted to sell fully self-driving cars to consumers outright, it would have to master all weather conditions before it could sell its first vehicle, since customers might want to drive their cars to wintry states.

But it's not a problem if a self-driving taxi in Phoenix can't handle snow, icy roads, or heavy rain, since these conditions happen so rarely in the area. Once its Phoenix service is established, Waymo will be able to expand to places like San Diego, Los Angeles, and Las Vegas, where the climate is similar, working its way north and east as it gets better at handling rain, snow, and other environmental challenges.