While there are thousands of slot canyons in the American Southwest, very few of them are as accessible and beautiful as the Narrows of Zion National Park. The canyon is still being cut each day by the North Fork of the Virgin River, and this is exactly what can make exploring here so tricky. Whether you are heading for a day hike or a multi-day trek, you will want to keep a few very important things in mind.
The same thing that makes this hike unique is what makes it dangerous. The Virgin River can swell at any given moment. A flash flood killed a group of seven hikers in a tragic event during the fall of 2015 in nearby Keyhole Canyon. Storms do not need to be very close to send ample water to inundate these tight spaces, and they can come up unexpectedly. After all, weather is still unpredictable, even with our improved tracking and prediction. It is very important to be weather conscious and to check with the rangers before doing this hike.
Take the shuttle to the Temple of Sinawava at the end of the main canyon's road if you are just doing a day hike, the most common choice. You will not need a permit and you can turn around at any point, although it is recommended to at least make it to Wall Street which is two hours in. If you want to do the full 16-mile overnight, you will need to get a permit for the lottery. You'll start at Chamberlain's Ranch, which is at the top of the canyon. There are 12 campsites available for overnight hikers.
If you are day hiking in the late spring, summer, or early fall, you can get away with not having canyoneering shoes and neoprene socks. Any other time would require some gear to stay warm; this can extend to wet suits or even dry suits. You can rent anything you might need from Zion Adventure Co. Footwear is the most important aspect along with having some sort of a stabilizer such as hiking poles or a walking stick. There are free walking sticks at the trailhead that are on a "take it in and leave it when your done" basis for the day hikers.
This can be tricky. For instance, the summer months are popular because the water is warm, but the storms that cause floods are more frequent and the hike is crowded. If you are day hiking in the summer, make sure to get on the first shuttle to avoid the heavy crowds and high temperatures. Spring has less of a flood risk from rainstorms, but can be shut down if the snowmelt gets the river flowing above 150 CFS. Autumn has less storms than summer, but it can start to get a bit colder. That said, autumn might be the best time period overall. If you go in the winter, you better be prepared for near-freezing water conditions.