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Re: [John Muir Trail] leaving for JMT fri 8/31

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  • John Ladd
    ... See this folder http://groups.yahoo.com/group/johnmuirtrail/files/Weather/ Open the file Weather - night temps ... I assembled a complicated graphic
    Message 1 of 6 , Aug 27, 2012
      On Sun, Aug 26, 2012 at 10:03 PM, Linda Jagger <lindajagger@...> wrote:
      I'm told its usually pretty dry, sunny. what should we expect for lows and high temps?

      See this folder

      Open the file "Weather - night temps ..."  I assembled a complicated graphic showing 10 years of nightly lows at two locations along the trail. Most nights are mild, but there are occasional nights most years in almost any month (incl September) where you will see temps in the below freezing area (though not much below).  (Note, this file is a bit complicated to follow on the screen - it is best to print it out)

      I don't have a chart of daily highs. But mostly you deal with temps in the 70's.  Some sun-exposed southern-exposure climbs can get hot, though.

      As you have heard, we are mostly dry, save for the common short, intense afternoon thunderstorm that can be quite refreshing.  Kind of like a kid playing in a sprinkler after a hot day.

      But there are occasional long rains overnight and sometimes the usually brief afternoon thunderstorm will persist for hours.  Three friends and I sat out one on August 14 (this year) on the PCT about 200 miles north of the JMT (near Carson Pass) and several of us went near-hypothermic.  We were pinned down in some trees (the lightning precluded moving as we'd be covering dangerous open areas). The temp dropped from mid 70's to very low 50's.  The rain was icy cold and mixed with hail and very, very heavy for over 2 hours. (A nearby weather station recorded 1.5 inches of rain) While it wasn't super-windy, the combined effects of wind chill and the simple cooling effect of having raingear constantly re-wetted with cold water made it very, very cold. We were all intentionally inducing heavy shivering to keep warm. (I had extra insulation layers but didn't want to get them wet, so left them in the drysacks until the storm was over. Later, I was happy I had, because I could at least warm up with dry layers after the rain stopped.) 

      I strongly encourage people to bring adequate raingear (including rainpants) for a severe storm, preferably something like Goretex Paclite.  Heavy storms are not frequent, but you need to deal with them.

      BTW, my three companions got so cold and discouraged by this storm that they bailed on their trip after this storm, though they were experienced and tough backpackers with many trial miles under their belts.  I think that their lightweight gear inclinations contributed to their bailing on me. (Only one of the three had good raingear and none of them had as many still-dry insulation layers as I had with me)

      John Ladd
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