I'm planning a Southwest USA tour that can only take place in late July to early August. Roughly speaking, it's San Francisco, Yosemite, Death Valley, Las Vegas, Zion NP, Monument Valley, Grand Canyon NP, Havasupai, Los Angeles.

I've read that this is when most rain falls, though it is a desert after all, so I'm sure how much rain there really is.

As part of this tour, I'd like to hike down into the canyons.

Specifically, Havasupai in Arizona (a side canyon of the Grand Canyon), and The Narrows in Zion National Park.

I realise that if there is heavy rain then this can lead to flash flooding, and then these canyons would be closed/ evacuated.

What should I do?

As it's high season, life will be easier if I have pre-booked accommodation. Having never visited this region, though, I don't know how crucial this is.

If I pre-book everywhere and I get to the canyons, I'm kind of stuck. I can't 'skip and move on'. I know I could find an alternative for the day or two, but I'd really rather not. Another potential option is to 'save up' lost days and (doing the tour in reverse), make a detour to the Humboldt Redwoods State Park.

If I don't book, could I risk wasting lots of time and money finding a hotel? Note: I would consider camping for, say, half of the nights.

Anyway, how likely is 'rain so heavy that it prevents canyon entry' anyway? Should I really be that worried?

Cheers :)

  • Given recent droughts... I wouldn't worry about it all. Commented Jul 19, 2014 at 19:56
  • 1
    Droughts can actually both worsen the flash flooding itself as well as the damage done by the flood.
    – CGCampbell
    Commented Sep 4, 2014 at 16:54

2 Answers 2


If you're in a canyon or gully and it starts raining hard (> 5 mins), get to higher ground ASAP. This should be obivous, but perhaps not. Most serious trouble from flash flooding come from people camping in a gully and some distance away, the rains come off a mountain in a flood. Preventing this is a bit harder, but still not difficult. Look around for rainstorms on the horizon, especially on nearby mountains. The rain can saturate the ground and rush down the channels on the mountain, flooding gullies even miles from where the rain fell.

In short, keep your eyes open, watch for rain.

  • 1
    The problem with canyons and gullies is that the rainfall inducing the flash flood is more likely to be occurring completely out of the sight of the area of the flood.
    – CGCampbell
    Commented Sep 4, 2014 at 16:56
  • Perhaps at the bottom of the canyon, but at the rim? The storm should be visible by looking upriver. Unless we're talking a bibical rainfall event, the rain should be visible from an elevated spot.
    – nielsonm
    Commented Sep 4, 2014 at 17:28

That's a pretty ambitious trip you have planned. How long are you going for?

The Narrows are dangerous in bad weather but Zion National Park will have very good weather reports and info as to whether it is safe to go into The Narrows. The rangers probably don't allow entry if there is any risk. There is plenty to do in Zion if you can't go into the narrows so don't worry about prebooking. Actually, it is a good idea to book as early as possible here, even for campgrounds, because it is a very popular area.

Not sure about Havasupai; haven't been there yet.

If I were you, I would save Monument Valley for another trip, and add Bryce and the North Rim of the Grand Canyon (instead of the South Rim) on the Zion part of the trip.

On the way back to LA, if you drive through Las Vegas take some time at the Valley of Fire State Park. If you go that way, the Mojave National Preserve short Rings Trail is excellent.

More on flash flooding: Main roads will have bridges over "washes" that can flood and you will drive over these in good weather and wonder why in the world such a long the bridge was built over such a small trickle of water.

  • 1
    This question is from 2014, so I think it's like the OP figured something out. Your advice is great for future travelers though! Commented Dec 4, 2016 at 22:14

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