Joshua Tree National Park Warnings and Dangers

For current ozone concentration check the website below. Nothing like being above 4,000 feet with 90+ degrees and the maximum 8-hour average ozone concentration (ppb) is 93. Not a good time for some exercise.

So, as you can decipher from my username, I'm not one of the skinny "billy goat" kind of hikers that are prolific in Joshua Tree. I'm short and fat, and I hike very slowly. However, it wasn't physical limitations that made me despise the Mt. Ryan trail, it's my crippling fear of heights.
The Mt. Ryan trail is literally climbing a mountain. The trail is 2-3' wide at best, and for much of it there is a sheer drop off plummeting to the desert floor. There are rocks you have to scramble over, and, my worst fear as a hiker, much of the trail is made of big flat rocks with loose sandy gravel on top, making it very slippery.
Now you may ask, "Hey genius, what did you expect from a trail that says mountain right in the title?" That's a fair point, and I'm not sure what I expected, maybe, I don't know, oh, a trail! I certainly didn't expect to have the grim reaper as my hiking buddy.
For lots of condescending hippies who passed me on the trail it seemed like they had a good time. So if you're a condescending hippy and have an absurd lack of understanding of the properties of gravity then you'll probably love this trail.
For me, and my fellow hobbits, avoid Mt. Ryan at all costs. There are plenty of challenging and beautiful hiking trails in the world that don't make you ponder your mortality.

This is really to reinforce the advice given in leaflets and notices posted within the Park about following the Paths and the maps provided. Wear suitable walking shoes an clothing including a hat. We were there early in the year at the beginning of March and the sun was very strong - as can be seen on the faces of some of our party in our Accommodation and Restaurant Tips.
Also - carry water and refreshments with you! There are no outlets for these things in the Park and you may be glad of the water.

Temperatures in the desert in the summer can frequently reach over 100 degrees. The desert is also very dry. Make sure you drink plenty of water before, during, and after any outing. Remember the sunscreen and maybe a hat too.

Nothing says warning like a huge warning sign in red letters. Brushing against these plants will cause the needles to "jump" at you (hence the nickname "jumping cactus") There are a number of references to horror stories from park rangers who have had to help folks remove these extremely painful cactus needles. Just watch where you're going while among them, and you'll be fine!

Although the park is in the southern U.S. at times it can still get cold. It was below freezing when we were there but a simple zero bag will cover that. Once the sun comes up unless its mid winter you'll be fine in a tshirt. I did get sick which made the cold temperatures seem much worse.

Summer is hot. But it's also monsoon season, and you're likely to experience rain--possibly very strong rain. Cumulonimbus clouds look puffy, peaceful and pretty from the side. However, a lot of water can pour out of them, and if it pours out over a mountain, it can flow down to you in a flash flood. Learn to recognize such clouds--particularly anvil clouds. (They really do look like an anvil, because they're tall enough to reach the upper-level winds, which "blow their top.") If you see such a cloud, stay somewhere high. Don't go down into canyons, even if you stay on a ledge. The wall of water that passes through can be upwards of 40 feet tall.

I noticed a lot of animals darting across the road as I drove around. From rabbits, to jackrabbits, to birds, there were all sorts out and about. Keep it slow so that you don't end up smacking someone and making them road kill.