Iron's a beast. But I repeat myself.
First time I tried it was on a hot day in July. Not my brightest idea.
If you ever get in a bind on water, there are a couple of sources, but they're not exactly convenient. From Allison Saddle* there are two old trails leaving the saddle, one to the west, and one to the east. The trail to the west goes to the Allison Mine. There's pretty reliable water there, but like I say, it's out of your way.
The trail to the east gets you to water more quickly than the trail to the west. Also, the trail to the east is slightly less brushy, but the trail is pretty washed out in places. According to Zé's latest TR, one has to go down a slide about 200' before reaching the canyon bottom; the trail is simply gone.
Take a look at
this map. "A" marks Allison (aka Heaton) Saddle. "B," "C," and "D" mark the old trail to the east. One has to leave the route of the old trail around "D" and drop down a slide into the canyon. "E" marks the approximate point where water can be found. "F" marks the "NO TRESPASSING" sign on the NE boundary of Widman Ranch (private property). I've dropped down through the ranch, and I know other people have too, but a) you're trespassing, b) they have guns,

and c) it's shorter to just go back to Heaton Saddle and down the trail to Heaton Flats. There are also quite a number of stream crossings as one descends down Coldwater Canyon.
So, neither the Allison Mine nor Coldwater Canyon are terribly convenient, but by the same token nothing is worth becoming a heat casualty. In a bind, I'd go down into Coldwater Can. for water in a second.
HJ
*I've also heard Allison Saddle referred to as Heaton Saddle and Coldwater Saddle. FWIW, Heaton Saddle is the name by which John Robinson refers to it and the name by which I've always known it.