[pct-l] Weather Log

[steve_peterson at sbcglobal.net (Steve Peterson)]

This may be far more detailed info than you're looking for, but I have been 
delving into the weather records located at http://www.wrcc.dri.edu/climsum.html
(Click on N. California, S. California, etc.). You need a good atlas that will 
give you some towns close to the trail, but with perseverence you can get quite 
detailed information. I haven't completed my investigation, but I can give you 
the following:

(The format is: the dates I looked at (roughly the dates a thru-hiker would be 
in the area), the name of weather station, the average high, +/- 2 standard 
deviations, the low, +/- 2 standard deviations, and the chances of various temps 
around (just above, just below) freezing. All temps are in degrees F.)


Apr 25 - May 5 Campo, CA  74-76 +/- 20 deg, 38-40 +/- 12 deg 20-30% 29F, 10% 25F
May 5 - May 15 Warner Springs CA 75-77 +/- 16 deg, 36-38 +/- 8 deg, 20% 28F
May 5 - May 15 Idyllwild CA 67-69 +/- 18 deg, 37-39 +/- 8 deg, 50% 29F, 10% 24.5F
May 15 - May 25 Big Bear Lk CA 66-68 +/- 16 deg, 34-36 +/-5 deg, 70% 28.5F, 40% 
25F, 10% 21F
May 25 - Jun 6 Sandberg CA 71-74 +/- 18 deg, 49-55 +/- 16 deg <10% 32.5F
May 25 - Jun 6 Tehachapi CA 73-76 +/- 18 deg, 47-49 +/- 13 deg <10% 32.5F
Jun 5 - Jun 15 Lodgepole CA 63-67 +/- 18 deg, 36-39 +/- 12 deg 40% 29F
Jul 1 - Jul 15 Truckee CA 78-82 +/- 12 deg, 40-42 +/- 12 deg, 10-20% 28.5F, 
30-70% 32.5F
Jul 15 - Jul 30 Burney CA 87-89 +/- 14 deg, 42-44 +/- 13 deg, 20-50% 36.5F, 10% 
32.5F

A few notes on the locations:
  - Sandberg is located at the start of the trek along the aquaduct at about 
mile 516. It should be representative of the desert stretch.
  - Lodgepole isn't very close to the trail, but it's the only site for which I 
can find data at altitude near the start of the Sierras. It's at 6750' elevation 
  in Sequoia National Park (on Hwy 198) and roughly at the same latitude as Mt 
Whitney (mile 760).
  - Truckee is on I-80, just north of Lake Tahoe and is at 6,000' (mile 1153).
  - Burney is at mile 1409 and about 3,000' elevation.

A few comments on temperatures:
  - There is tremendous variation from year to year--averages mean almost 
nothing. As you may know, statisticians measure variation using "standard 
deviation". By definition one standard deviation includes 66% of the data (33% 
above the mean, 33% below) and two standard deviations include 95% of the data. 
The +/- numbers I quote above are TWO standard deviations. That means that 5% of 
the time, the temperature will be MORE extreme than I've listed. As you can see, 
you'll have to prepare for quite a range.
  - The geography doesn't make it easy for you to implement your strategy (one, 
which, BTW, I was hoping to utilize as well). South of the Sierras (i.e., from 
mile 0 to mile 700), there are stretches of desert interspersed with stretches 
of mountains. My guess is you'll want a 20-25F bag for the mountainous stretches 
(San Jacintos, San Bernadinos) and just have to put up with carrying a few extra 
ounces through the warm southern sections where you may not need it.

I have yet to explore in detail the temps for much of Oregon/Washington, but 
from what I've heard, people send their cold-weather bags north to Wash once 
they get north of, say, Sierra City (mile 1191). I hope this helps; feel free to 
email me off list if you want more.

Richard Hare wrote:
> Hello
> 
> Have any thru hikers kept a detailed log of weather conditions.  I've just
> been looking at some returners photos and they all look dry and Sunny (still
> I surpose not many hikers would get their cameras out in the rain! Duh!!)
> I'm particularly interested in minimum temperatures at night so I can work
> out a strategy for having warmer gear at cooler parts of the trail and less
> gear at the warmer parts.