Eclipse visitors should prepare for bad cell service. Here’s how.

Cellular networks sometimes bog down when people in one place all call, text, stream or post at once — like at a packed football game or, in this case, an opportunity to view a potentially once-in-a-lifetime total solar eclipse.

These congestion hiccups to cellular networks are far less common than they used to be. But just as eclipse tourists might want to prepare for traffic jams and portable toilet shortages, it couldn’t hurt to plan ahead for potential mobile disruptions, too.

Download, print or write down driving directions ahead of time

In case you don’t have mobile service for turn-by-turn directions, have a hard copy of driving instructions to wherever you’re going before or after your eclipse viewing.

Some apps including Apple Maps and Google Maps also let you download maps before your trip to find your way even without mobile service.

For Google Maps, put in the location where you’re going. Select your profile picture or initials in the upper-right corner of the screen. Pick “Offline maps” and then “Select your own map.”

Zoom in or out until you’ve highlighted the area you want to save. Tap “Download.”

Find that saved map again by following the same instructions. You can access turn-by-turn directions if your destination is in the downloaded map area.

For Apple Maps, search for the area where you’re traveling. Tap “Download” and zoom in or out to highlight the area you want to save.

You can access turn-by-turn directions even when you don’t have cell service. The only feature that won’t work without mobile reception is real-time traffic information.

Waze has more limited directions if you lose an internet connection during your drive.

Have a backup plan for emergency calls

Jacob Saur, administrator of Arlington County Public Safety Communications and Emergency Management in Virginia, suggested texting 911 in areas where that’s an option. He said texts are not typically as affected by wireless phone congestion.

Or if you can, call emergency services from a landline or a VoIP line that carries calls over the internet. If you’re in the range of a WiFi network, you can also route any mobile calls that way.

Lastly, some phone models have built-in options for using satellites to contact emergency services. Find out the options for your device before your eclipse trip.

This might not be necessary, but it doesn’t hurt to plan for emergencies.

Some payment terminals for swiping your debit or credit card use the same mobile networks as your phone.

It’s possible they could stop working if you’re somewhere with a flock of visitors on their phones. In case that happens, have some cash on you.

Plan ahead to entertain the kids (and yourself)

Some digital entertainment apps let you download videos or music that work fine even when you’re not connected to the internet.

You can find download instructions for Netflix, YouTube, Disney Plus, Spotify and Prime Video. (Amazon founder Jeff Bezos owns The Washington Post.)

You need to be a paying subscriber to Spotify’s and YouTube’s premium services to use those apps’ download features.

You can also download podcasts, e-books and audiobooks to your phone that will work without mobile service. (We love Libby for free e-books and audiobooks from some public libraries.)

Or ditch the devices and brush up on rules for the I Spy road trip game.

Why do mobile networks flake during temporary surges in use?

Phone companies have spent a fortune, especially in the past five years, expanding and modernizing mobile networks, including for sudden spikes of mobile use.

Still, in eclipse tourist zones, you might have service, but it could be far slower than you’re used to.

Patrick Halley, president and CEO of the Wireless Infrastructure Association, compared it to a wedding if there are five times the number of expected guests. You might have to slice the cake into tiny pieces that won’t satisfy anyone.

But many local officials have planned for eclipse-related mobile phone surges.

Some areas in the eclipse’s path have brought in scaled-down cellphone towers to handle more network use. (Delightfully, these are referred to by animal shorthand: COWs and COLTs, for cell towers on wheels and cell towers on light trucks.)

Everything could work fine. Officials in Carbondale, Ill., which was in the path of an eclipse in 2017 and again this year, were worried seven years ago about overloaded water and sewage systems, overwhelmed emergency rooms and strained mobile networks, said Steven Mitchell, Carbondale’s economic development director.

But while visitors from Chicago sat in terrible traffic on their way home after the 2017 eclipse, most of the worst case scenarios didn’t happen. “Cell service was not impacted at all,” Mitchell said.

If overloaded networks do stop you from posting your selfies immediately, Halley had some philosophical advice: “Maybe put the phone down and enjoy the eclipse.”