Snow, rain, and hail hit Interstate 80 as it passed over Donner Summit on Monday.
For trips through mountain passes, the California Department of Transportation, or Caltrans, recommends packing for emergencies.
"Bring chains, bring blankets with you, bring bottled water, snacks, things like that," said John O'Connell, Public Information Officer for Caltrans District 3, which covers 11 California counties, including Nevada County, where Donner Summit is.
O'Connell says trail mix and protein snacks are the best to keep with you just in case. You should also top off your car before your journey.
"If you're driving an electric vehicle, make sure it's charged before you [go]," he said. "If you're leaving Reno, make sure you [charge] it there. If you're going up in the west side, do it by the time you get to Auburn. Same thing with gas. Make sure you got a full tank of gas."
Speaking of charging batteries, O'Connell also recommends keeping your phone's battery charged.
Conditions can change quickly on mountain passes. The weather can be bad toward the summit even if it looks good on the way.
"The weather might be fine down in Auburn," O'Connell said, "but as soon as you get up towards Soda Springs, or where Boreal is, things can certainly change."
If conditions are hazardous, O'Connell says to drive below the speed limit and give other drivers space. It only takes one driver not following these rules to impact travel.
"We're not expecting any major traffic up there, but it only takes one incident for things to change," he said.
Finally, don't put all your faith in your GPS.
"If there is a road closure, do not follow your navigation telling you, 'Oh, this is a detour.'" O'Connell said.
You can track road conditions, chain controls, and closures through Caltrans QuickMap.
