Yellowstone geyser predictions: Why didn’t it erupt on time?

Visitors to Yellowstone National Park watch an eruption of Old Faithful Geyser from the boardwalk on Geyser Hill. (Janet White photo)

By Janet White

Geysers are a rare sight anywhere in the world, so with half the planet’s geothermal features located in Yellowstone National Park, the natural wonders rank high on “must-see” lists for most first-time park visitors. Old Faithful is famous for erupting “on schedule,” so shouldn’t there be a geyser schedule for the whole day posted somewhere?

Sure, if geysers were truly predictable. But they’re not.

It would certainly be convenient for park rangers to release a daily eruption schedule for all Yellowstone geysers. That would mean you could figure out when the fifth eruption of Old Faithful would happen, or when in the late afternoon you could walk down to catch Daisy Geyser in eruption. But all the rangers (or anyone else) can do is make an educated guess about when the next eruption might occur.

Prediction isn’t really an accurate word for what happens in Yellowstone with the geysers. A better and more accurate term would be a “forecasted window of opportunity” for the geyser to next erupt, with the predicted time falling in the center of that window. And some of those windows are fairly big. Grand and Great Fountain have 3- and 4-hour windows, respectively. That’s a lot of time to invest on your vacation when Yellowstone is so big and so vast.

It’s always a good idea to check at the Old Faithful Visitor Center to see when nearby geysers might be expected to erupt. But keep in mind that only a handful of geysers are tracked and forecast this way, and all are located in the Upper Geyser Basin except for Great Fountain Geyser, which is in the Lower Geyser Basin. They include:

• Old Faithful Geyser – 20 minute window (+/- 10 minutes)
• Castle Geyser – 2 hour window (+/- 1 hour)
• Grand Geyser – 3 hour window (+/- 90 minutes)
• Daisy Geyser – 1 hour window (+/- 30 minutes)
• Riverside Geyser – 1 hour window (+/- 30 minutes) 
• Great Fountain Geyser – 4 hour window (+/- 2 hours)

These forecasted windows of opportunity are generally wide enough to capture most eruptions, but geysers (being geysers) always seem to toss in a curve ball now and then by erupting outside of their prediction window.

Calling Old Faithful

You’ll want to see Old Faithful, and now you can just call the Visitor Education Center and listen to the recording as soon as you get in cell range. As you’re approaching the Old Faithful area, call 307-344-2751 and then press 1 when prompted. Cell phones also typically get decent reception in most of the other major developed areas in Yellowstone.

Online resources

The Park Service has many good sites to help you learn about the various types of thermal features and the different places in Yellowstone to see them.

There are also a number of great geyser websites not affiliated with the National Park Service:
Geyser Times
Geyser Watch (Disclosure: I produce this site)
Geysers.net
GOSA – Geyser Observation and Study Association

The Serendipity Approach

You can always take the “serendipity approach,” which simply means walking the geyser basins and seeing what decides to erupt. It also means pausing to wait for a geyser if a sign lets you know an eruption might occur soon, or if a geyser enthusiast tells you it would be a good idea to stay because they’re seeing some positive signs.

No matter what approach you take, keep in mind that geysers are a part of nature, and don’t operate according to our schedules, and your visit to the geysers and hot springs in Yellowstone will be a memorable one.