What caused the massive flooding and mudslides in Yellowstone?

Rain and snow combined to create intense flooding across the beloved park

Thousands of visitors were evacuated from parts of Yellowstone National Park this week after heavy rain brought flooding and mudslides to the country’s oldest national park.

The most recent update from the park states that the northern area — which was hit hardest by the floods — will remain closed until further notice. Park officials say the southern area, which includes spots like the geyser Old Faithful, could be open sooner but will be closed at least through the weekend.

The flooding was due to a combination intense rainfall and heavy snowmelt, the Associated Press reports.

Parts of the region saw up to five inches of rain from Friday to Monday, the National Weather Service (NWS) says. In addition, the region saw multiple inches of snow-water equivalent melt — a measure of water contained in melting snowpack.

Reuters reported that the area also saw warmer temperatures earlier in the week, which accelerated snowmelt from the park’s high peaks. Per US government data, the area currently has a lot of water piled up in snowpack, Axios notes.

Floodwater continued to move downstream, affecting parts of Montana further from the park, AP reports. Residents of Billings were asked to conserve water after the city had to shut down its water treatment plant due to flood conditions, they add.

Images from the park this week showed road and building damage as water poured into valleys and pushed rivers far above normal levels. On Monday, the Yellowstone River in Corwin Springs, Montana surpassed its previous record high water level by at least two feet, according to the US Geological Survey.

“We will not know timing of the park’s reopening until flood waters subside and we’re able to assess the damage throughout the park,” said park superintendent Cam Sholley via a statement. “It is likely that the northern loop will be closed for a substantial amount of time.”

There were concerns among some locals that closures and damage would depress revenue from tourism, AP reports.

The climate crisis is expected to increase the frequency and severity of events like rainstorms in many parts of the country. Over the past few decades, more and more precipitation across the US has come via extreme one-day events, according to the US Environmental Protection Agency.

In Yellowstone, climate change could lead to things like more wildfires and reduced snowpack over the 3,400-square mile reserve, according to the National Park Service.