Trying to get a sense of what the avg. minimum nightime temps might range during the last week of Sept and first week of October on the JMT in order to plan sleeping gear.

Anyone have experienced at this time in the Sierras that they can share?

30's for sure most nights and I would be prepared for 20's or possible high teens if a front blows through.

-H

http://cdec.water.ca.gov/staInfo.html

Have fun

My BIL Dave and I take an end-of-September, first-of-October Sierra hike every year since 2004. JMT in 2005 and 2006. It has become a tradition as we love the way that anything and everything weather-wise happens and the people are mostly gone.

I have logs of many lows in the teens. It has snowed on us every year, once three days that chased us out early.

Raymond,

Thanks for the comments. I hope others like yourself chime in. Although it's a bit anectdotal it sounds like you've kept some records..
Like you, I enjoy the fall. I chose this time of year to go to the sierras to get some more variety in the weather mix and to avoid the crowds. Work is also covering my airfare since I have business in Sacramento around then too. Last year I was on the CDT in Montana...same two weeks...we got a bit of snow and night time temps in the 20's. Very enjoyable.


Jeff,

Yes I've already started looking at the CDEC. It's a bit of a task to determine the stations that have long term temp records vs. the snotel stations that just have snow courses. I'm not as familiar with the geography of the Sierras so i thought I would see if anyone had personal experience. I did get a 7 year stretch of data from the Central Sierra Snow Lab at around 7000'. From 2002 -2008 avg min air temp there was 38F. Some recent research seems to indicate the sierras are getting a bit cooler and the central valley much warmer, possibly climate change exacerbated by changing land cover in the valley: http://cat.inist.fr/?aModele=afficheN&cpsidt=17578376

So it may be that a time series based on the last 10 years will be more representative of what to expect???




I'm also not quite sure what elevations I'll be sleeping at yet which will ahve a big influence on air temps as well as microclimates...most of the temp records seem to be at lower elevations.

Anyways I'll be digging around into the station data more in the coming weeks.

Anyone have links for places to look for short and semi long term weather reports...NOAA is always a mess to navigate and seems to vary region by region as to what they have and where it's kept. As I get closer to my trip I'll benefit from knowin g where to find the most recent forecasts.

Insulation wise I'll likely have a WM ultralite, bivy sac, thin evazote pad with a new thermarest neoair + a Montbell thermawrap parka for extra insulation. I'm thinking that should be enough. to take me into the high teens.

"Anyone have experienced at this time in the Sierras that they can share?"

Mid teens to mid 20's from Forrester Pass down to Crabtree Meadows, IME.

Maybe high 20's (in Sep anyway).

However, I've been down below freezing every single time I've ever gone into the high Sierras.

This is about 15 times and only 3 of those have been outside of May-Sep.

I would expect the nights to be below freezing. I typically have planned to be comfortable in the 20s F, safe to 0F, and prepped for a moderate amount of snow.

The lowest I have seen in Sept was 10.2F on a father/daughter trip several years ago... though I know people who have experienced colder temps in Sept/Oct.

State of california water resources board have instruments in a number of locations along the JMT. For example data for tuolumne meadows sep-oct 2008 can be see at the url
http://cdec.water.ca.gov/cgi-progs/queryDaily?TUM&d=01-Nov-2008+00:24&span=2month

Edited by verber on 06/07/2009 01:37:34 MDT.

>> I would expect the nights to be below freezing. I typically have planned to be comfortable in the 20s F, safe to 0F, and prepped for a moderate amount of snow.

Excellent advice. Jul 31 1997, I got snowed on just above Mammoth Lakes at around 9,000 feet.