The United States Geological Survey (USGS) monitors Virgin River flows and measures water volume in CFS, or cubic feet per second. The CFS of the Virgin River fluctuates over time, rising or falling as a result of rains, snow melt, and air temperatures. Zion National Park uses the current CFS reading as a reference tool to gauge safety conditions in The Narrows and regulate access.

The Park does not issue Thru-Hike permits when flows exceed 120 CFS, nor do they allow hiking from the Bottom-Up when flows are greater than 140 CFS. Narrows closures last for 24 hours AFTER the river has surpassed a particular cut-off benchmark. For example, if snowmelt causes the river to peak at 155 CFS at midnight, The Narrows will be closed until the following midnight, even if the river flow is 110 CFS during the entire day. This can be a common predictament during the spring thaw, as the hot afternoon sun melts copious snow, which takes 6 - 8 hours to reach The Narrows. Snow stops melting and re-freezes by evening, vastly reducing river volume by the next morning... but the 24-hour rule restricts hiking for the day.

To study current or historic Virgin River flows, click here to visit the official USGS site. Remember, 120 CFS and 140 CFS are the key benchmarks pertaining to whether The Narrows is open for hiking and/or backpacking.

Use the chart below to estimate the hike-ability of the river today. For ninety percent of an average year, the Virgin River flows less than 75 CFS, making it hikeable for any person weighing 50 pounds or more.