Right now in Palm Springs, at 9.23 at night, it's 96 degrees. It was 108 today. I agree KathyW, that although forecasting is much better than it used to be, but still, there is a margin for error. Zippety, thanks for the NOAA link, loved that groovy hour by hour thing!

I think it's a questionable forecast, though, and don't think ziplinesd should rely on it. FOUR other forecasts (Accuweather, Weather Underground, Weather Channel, and the local news meteorologist) have the day variously at 101/73, 97/64/, 98/68, and 97/64.
When your safety is at stake I think it's better to think pessimistically and take the worst forecast, in this case Weather Channel's 101/73. That to my mind is a dangerous number and I wouldn't recommend anyone venture out in those conditions. Even a three a.m. start time is doesn't make you safe--suppose you get a slightly late start (most people do, so let's say 3.30), and hike up for four hours. The hike is much harder than you'd anticipated, or you get a little lost below the picnic tables, and 7.30 finds you only at five thousand feet (I know, it's probably impossible for Zip or Fern or Bluerail to imagine this, but it certainly isn't hard for me!) Then something bad happens--you start vomiting, a knee gets blown, or one's hiking partner just says he or she can't go on.
As I said above, what is our imaginary hiker going to do? It's ALREADY too late to turn back. Coming down Skyline takes every bit as long as going up. I don't know what the exact cut-off time is to turn around, but I know that one time in July (108/78, with humidity) I made the mistake of going up for a partial hike on Skyline, planning on turning around at 6.30 am (which I did), the idea being I would be back down at the parking lot by 8.30 (which I was.) I thought that was being safe. I literally almost did not make it. By the time I got to my car I was bright red and wringing wet. I was sick and screwed up the rest of the day. Had I been just a half hour later, I think I might have passed out on the trail and not made it.
Another time (years ago) I did Skyline in June, and at around 4500 feet started realizing I was feeling ill--nausea and the runs. I looked at my watch and saw it was eight o'clock. That was when I suddenly 'did the math' and realized with horror there was no way I'd make it down in time, that it was far too late. So I sucked it up, pretty literally, and somehow climbed four thousand more feet with food poisoning. Oh wasn't that a fun day!! By the traverse I was literally holding onto trees to stand upright. Oh yes, and I also had no water the last two hours. By the grace of God I somehow made it. My point here is for others to learn from my profound stupidity and not repeat my ignorant mistakes. When people who know Skyline well and have done it multiple times in various weathers decide to risk a high-temp day, that's one thing, but what concerns me is people who haven't done Skyline at all, or only a few times, who try it on a high-temp day. They just don't understand the risk they're taking and that's why I'm trying to convey in this post.
Ziplinesd, do you really have to do C2C this weekend? Can't it wait until a better time, i.e.the fall ? As I said, a three a.m. start time in no way makes you safe. Sure, that's a good start time, if NOTHING GOES WRONG. But what if it does?? Have you done C2C before, or recently? If you haven't, you should definitely wait until cooler weather. This weekend is not the time to discover your conditioning isn't up to this incredibly challenging trail, which Zip correctly compares to a marathon.
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