Grand Canyon's Danger Months
The Weather Planner at GrandCanyonHiker.com no longer includes the table for the Grand Canyon's "Danger Months". I've captured this table from the Google cache before it is gone forever, because I think that it's good, important information.
I can only speculate about why they removed the table, but I suspect that they don't want to be seen as encouraging hiking in those months. Neither do I. Even in May, when we are hiking, the Inner Gorge can be hot. Note especially that the "High" temperature in the table is an average daily maximum. Not all days are average. About half of them are hotter, and it is especially important to be prepared with the proper water supply during the hike, the proper educational preparation before the hike, and the proper mental attitude during the hike. Do not charge ahead just because that's the way you envisioned it when you set out. You can always chill out at the river, creek, campground or other shade and wait out the heat. It may be dark when you get out, but heat exhaustion is dangerous, and heat stroke is deadly.