Re: [John Muir Trail] What Can We Expect Above Tree-Line in August?
- It could drop into the 30's above 10K elevation. Sometimes even worse depending on weather. The Sierras tend to make their own weather.
From: mattmillea <matt@...>
Sent: Tuesday, July 23, 2013 1:14 PM
Subject: [John Muir Trail] What Can We Expect Above Tree-Line in August?
First time to the trail, we are going to be in Evolution Basin area. How cold is it there at night in early August?
- Likely in the 40's, possible to get into high 30's. Campsite selection will impact temperatures as katabatic winds move down the basin.Dave
- I was there two years ago. Mostly mild down in the canyons at night, such as along Evolution Creek or down in Big Pete's meadow. Camped at the lake above timberline is different. Early in the morning it was just above freezing. Hiking pants, Long sleeve light wool zip-T, long-sleeve nylon shirt, down vest, light wool cap, light gloves were perfect. Once the sun is up, the temps rise fast. If it were raining and overcast, temps probably wouldn't drop as low, but the air will be chilly throughout the day. If it were windy and clear, add a wind/rain shell to the above layers and you'll be fine. Of course, once you hit the trail you will begin to peel most of this stuff off.
--- In firstname.lastname@example.org, "mattmillea" <matt@...> wrote:
> First time to the trail, we are going to be in Evolution Basin area. How cold is it there at night in early August?
- On Tue, Jul 23, 2013 at 2:15 PM, David Neumann <idmtman@...> wrote:Likely in the 40's, possible to get into high 30's. Campsite selection will impact temperatures as katabatic winds move down the basin.DaveI agree Dave is generally right, but you can get nights near or even below freezing, though not likely. There's a chart of nightly lows over 10 years in the files area if you want to get exact.Going by memory only of that chart, even August can occasionally have a night noticeably below the high 30's. Only necessary for your worst-case thinking and you can deal with that by clothing (or an emergency mylar blanket) inside a bag, even if it is not really designed for 30-ish temps. Mostly not all that cold.As Dave mentions, in some bowls you can sometimes find warmer sites upslope from a local bottom, as cold air can sink and collect at night if it doesn't find enough of a path further downhill (e.g., lots of uphill terrain but a narrow exit).And as Robert mentions, it is the clear nights that get coldest. Clouds hold in the heat.