The driverless cars of tomorrow may be programmed to deal with harsh winter conditions, inattentive pedestrians, or even bird poop, but the biggest hazard may be a solar storm that knocks out GPS communication and turns roads into giant parking lots.

According to a report in Bloomberg, space meteorologists are cautioning that over-reliance on satellite data could cause problems for self-driving or autonomous vehicles in the event of a solar disturbance. We usually don’t notice solar storms, other than the colorful auroras in the sky as charged particles collide with the upper atmosphere, but they can be disruptive to communications.

Solar storms, like hurricanes, are rated on a scale from one to five, and the NOAA regularly issues alerts about “space weather” that includes solar activity. Scott McIntosh of the National Center for Atmospheric Research says that space weather forecasts may become as commonplace as terrestrial weather predictions.

“There is a lot riding on this, from an actuarial point of view,” he said. “All it is going to take is a couple of accidents.”

NASA has two STEREO (Solar Terrestrial Relations Observatory) spacecraft monitoring solar activity, and the Air Force launched the C/NOFS (Communication/Navigation Outage Forecasting System) several years ago specifically to forecast possible disruptions to communication and navigation systems.

Luckily, we seem to be in a lull of solar activity as driverless cars take to the streets. The eruptions generally follow an 11-year cycle, which last peaked in 2014.

For their part, engineers of automated cars and trucks are taking steps to cope with unexpected disruptions like space weather. Some self-driving systems include onboard data such as regional maps that would let cars find the next freeway exit.

Danny Shapiro of Nvidia says that there’s enough redundancy built into self-driving navigation systems that fears of a Mad Max scenario on an interstate caused by solar activity are overblown. At the very least, the car would just pull to the side of the road and stop. Most cars aren’t overly reliant on GPS data when navigating across town.

“With very detailed measurements like lane changes and bike lanes, you don’t have time to take all this data and send it up to the cloud and back,” Shapiro said. “You go to the cloud when you’re asking, ‘Hey, what’s the fastest route to Starbucks?’”