What is the best time to hike Zion Narrows?

I LOVE slot canyons and Zion Narrows hike is something on my To-do for very long time since I saw it in a documentary and IMAX. So when I saw this deal from Southwest about 50% off on all travels my first thought was to book tickets to Las Vegas (nearest to Zion) or SLC. Due to restriction on this deal the travel needs to be completed by May 31st.

So the question: Is last week of May the best time to do Zion Narrows? I've fanatically looked for answer all over and here's the summary. Disclaimer: that I haven't been there so all these research comes from web, not my experience.

My criteria for "best time" is fairly simple:

  • Avoid wearing dry/wet suit to do this hike
  • Avoid wading in 1ft of water for miles
  • Pleasant 70s temperature that allows good other hikes like Angel's Landing

Several websites have various opinions on "best time". A top Google hit puts up a table indicating May, June and Septembers are the best. This is way too fuzzy answer because early May is actually as worse as April and it doesn't tell you different late May really is compared to late June. Yes, there is a big difference!

Next, other websites gets more specific and tells you late June and late September is the best time. We are getting closer to a specific answer but still no data points.

After lot of searching I finally hit the pot of gold:USGA Water Data! This website has exact numbers for CFS (cubic foot per second) and gage height data for each day all the way back to 1988. The rules are quite simple: anything below 50 CFS is easy and 250 FS is too much. The USGA has done fantastic job in presenting this data on website. For example, here you can see CFS levels for 2008:

NorthForkVirginRiverDischarge

Now you can see late May is not all that good but it is rapidly getting better over entire June although it takes all of the June before we get 40 CFS. This means late June is pretty good time to go but difference between early June and late June is almost two fold! Then notice all those spikes in early July. My guess is those are flash floods or thunderstorms. On other hand look how stable mid-end September is! We get 30 CFS almost all month.

NorthForkVirginRiverGageHeight

So we are looking at about foot of water at May end and about quarter of that in mid-end September.

Likewise you can go through charts for may years back. It obviously varies from year to year. For example, year 2007 had very low stable CFS at end of May unlike rapidly decreasing high levels of 2008.

For the past few years worth of charts that I checked one theme emerges: mid to end September has most stable and low CFS!

But how about temperatures? Here's where Weather Underground's seasonal average feature helps! Here is the seasonal averages weather graph for Zion National Park:

NorthForkVirginRiverWeather

As you can see, the temperature in mid-September is pleasant 70s just like in June.

So there you have it! Mid September to September end (2nd and 3rd weeks of September) is the best time to go to Zion National Park and Narrows. That's when you are most likely to get stable low water levels.