There's a noticeable trend among the cities Waymo looks to for expansion: snowier weather.

This week, Waymo announced it would begin an exploratory phase in Denver and Seattle. The company also made progress to start operations in New York City.

Waymo currently services cities across warmer regions like the Sun Belt. It's available in Phoenix, Austin, Atlanta, Los Angeles and San Francisco and is officially expanding to Miami, Dallas and Washington D.C.

Waymo, which is owned by Google's parent company Alphabet, is a frontrunner in the budding robotaxi industry since it debuted in Phoenix in 2020. But now as it looks to expand into more cities across the U.S., the question is whether their vehicles can, well, weather the cold climates.

It seems like Waymo is ready to test it out in Denver.

As Denver drivers would know, the city's roads have various obstacles much of the year from cold winter storms: slick roads after snow melts refreeze at night, strong winds, pot holes from the freeze/thaw cycles and large hail to non weather-related difficulties like construction along East Colfax Avenue.

Denver is the 17th snowiest city in the U.S. with a population of more than 10,000, according to the The Old Farmer's Almanac. The city gets an average of 57 inches per year.

The company said it wouldn't serve Denver customers right away, but will begin testing and working with local officials in an exploratory phase.

Denver to soon have driverless rideshare vehicles moving about its streets

Waymo said it would deploy a mixed-fleet of its all-electric Jaguar I-PACE with its fifth-generation driverless technology known as Waymo Driver and Zeekr RT vehicles with the sixth-generation edition.

"Our next-generation system is informed by years of winter weather experience across Michigan, New York, and the Sierra Nevada and engineered to autonomously sustain operations in harsher climates," Waymo said Tuesday.

Its fleet arrived this week and will start out in the heart of the city in downtown, Cherry Creek and the River North Arts District, according to the company -- though it plans to operate in the wider metro area. Service could begin as soon as next year.

Curtis Walker, a project scientist based out of the National Center for Atmospheric Research in Boulder, said he always wondered when Waymo would get into regions outside of the Sun Belt to challenge its driverless technology in more complex urban environments.

"And indeed, the day has come where they are at least attempting to go beyond," Walker said.

Driverless cars have long struggled with harsher weather. Does this mean the technology is getting better?

Just like with humans, snow and rain affects the senses of driverless cars. Camera sensors can be blocked, lanes are less recognizable from the accumulation of snow and other drivers are less visible.

Walker specializes in transportation meteorology and worked on a research project with NCAR in 2022 to look into how autonomous cars can be better designed for various weather conditions. He said there's been many technological advancements in the industry to solve those problems that have uses for not just Waymo, but companies working to advance autonomous trucks or freights.

An increasing number of driverless cars are relying on lidar and radar sensors to supplement camera sensors when they can't see due to rain or snow, Walker said.

"Those other sensors can actually see how close you are to an object in front of you," he explained. "Or even tell you things like has the vehicle out of your line of sight stopped in front of you so that you don't hit the back of them."

There's also a push to turn driverless cars into mobile weather observations, Walker said. Instead of relying on a fixed weather station like the one at Denver International Airport -- which is way out in the plains -- to calculate what's happening downtown, driverless cars could map out hyperlocal weather information street by street.

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"You don't have to guess, hey, is it raining a mile down the road," Walker said.

Waymo uses inference-based computations from its vehicle sensors to make decisions on the state of the weather, he said.

Waymo has operated in San Francisco fog, though it struggled during heavy fog in 2023 after several of their cars pulled over and impeded traffic. It also has navigated dust storms in Phoenix.

"Obviously, fog and dust are very different than snow and ice and blizzard conditions," Walker said.

When questioned by Boston officials, Waymo's Director of Product Management David Margines said Waymo isn't ready yet to operate for winter weather -- at least not without a human on board.

"We have not yet validated the Waymo Driver for fully driverless operations in things like snow and standing snow on the ground," he said in July, as reported by The Boston Globe.

Using artificial intelligence, Waymo said it has been teaching its software to detect snow and freezing conditions. But like a teacher, Waymo has to test and check if the cars comprehend what it learned in a process called validation.

The newer generations are trained for harsher weather conditions but still need to be validated, Waymo said. And going on more road trips gives the company more data to distinguish and learn from different types of winter driving conditions.

So don't expect Waymo to drive to ski resorts through Interstate 70 during a snowstorm anytime soon, Walker said.

Waymo will have to adjust to Denver driving culture, and vice versa

Morteza Lahijanian, associate professor at the department of aerospace at University of Colorado Boulder working on developing algorithms for autonomy said he was at-first excited about Waymo's expansion into Denver.

"After the excitement, I paused," he said. "How are they going to deal with all the weather uncertainties that we face in Denver, or in Colorado, in general?"

The big question, he said, will be how does Waymo's sensors differentiate items or read road signs when everything is covered in snow? Also how will it handle hail that could potentially damage sensors placed on the roof?

Waymo has to do more testing, he said.

And not just so Waymo adapts to Denver's car culture, Lahijanian said, but it's also important that Denver drivers get used to seeing Waymo cars on the road.

"It's a little weird to see cars without drivers," he said about visiting San Francisco and seeing them for the first time. "But now when I travel there, it's part of the city culture and nobody looks at them anymore."

While he's cautious, Lahijanian said he's still optimistic about Waymo bringing driverless robotaxis to Denver.

Part of what's made Waymo successful in the field is their slow and careful approach compared to other companies who are rushing to push things on the market that aren't ready, he said.

"It looks like they're going to run a pilot program. And it looks like they've had some experiences driving in harsh weather. So those are all good signs," Lahijanian said. "But we have to see how it unfolds."