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Sierra weather in September

 

I finally get a permit for backpacking JMT SOBO from Lyell Canyon to Mt Whitney! ?
My trip will be from 8/23 to 9/15(hopefully will be finished a few days earlier). A friend told me that the Sierra weather may be unstable in September, especially in Whitney area. I have backpacked in Sierra in the last week of September in 2022 and 2023 (Thousand Island & Yosemite) and the weather was perfect in those trips. But I am not sure how it would be in high Sierra mountains. May I get some information from you JMT veterans? Thanks!

Jingbo
 

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September is my preferred month. The earlier season daily afternoon thunderstorms, mosquitoes, snow and high water are usually gone.?

There is the possibility of a tropical storm passing through which brings significant rain like last year, or just a couple of days of rain.

It starts getting colder later in September with nights going below 20 deg F and there may be snow.

On 3/12/2024 8:16 AM, Jingbo Ni wrote:

I finally get a permit for backpacking JMT SOBO from Lyell Canyon to Mt Whitney! ?
My trip will be from 8/23 to 9/15(hopefully will be finished a few days earlier). A friend told me that the Sierra weather may be unstable in September, especially in Whitney area. I have backpacked in Sierra in the last week of September in 2022 and 2023 (Thousand Island & Yosemite) and the weather was perfect in those trips. But I am not sure how it would be in high Sierra mountains. May I get some information from you JMT veterans? Thanks!

Jingbo


--
Frank
 

Thanks for the info. Surely we must prepare for the rains.
I have limited experience with backpacking in the rain. Last year in early September I backpacked in Alaska Talkeetna mountains for a week. Only had two hours of sunshine the whole trip. After the first day it rained all the way to the last day. Fortunately in the most heavy rainy nights we stayed in huts built by Alaska Alpine Club, so we actually had only two nights of camping in the rain.?

On Tue, Mar 12, 2024 at 10:23 Frank <frankdpct@...> wrote:

September is my preferred month. The earlier season daily afternoon thunderstorms, mosquitoes, snow and high water are usually gone.?

There is the possibility of a tropical storm passing through which brings significant rain like last year, or just a couple of days of rain.

It starts getting colder later in September with nights going below 20 deg F and there may be snow.

On 3/12/2024 8:16 AM, Jingbo Ni wrote:
I finally get a permit for backpacking JMT SOBO from Lyell Canyon to Mt Whitney! ?
My trip will be from 8/23 to 9/15(hopefully will be finished a few days earlier). A friend told me that the Sierra weather may be unstable in September, especially in Whitney area. I have backpacked in Sierra in the last week of September in 2022 and 2023 (Thousand Island & Yosemite) and the weather was perfect in those trips. But I am not sure how it would be in high Sierra mountains. May I get some information from you JMT veterans? Thanks!

Jingbo


--
Frank

 

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There have been years where September in the Whitney area, especially late September, are _very_ cold. When I finished the JMT last week of September 2019, the last two/three days were below freezing, even during the day. Logistics, like keeping water liquid, can catch one by surprise. Another thing to remember about September is shorter days. The “Pickup at the Portal” episode in my podcast gives details of my experience. (I believe late September 2019 was anomalous as far as extremely cold weather in the Whitney area.)

?-Jim Z


 

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Congratulations Jingbo! I think you’re going at the perfect time. I’m one who would gladly trade a higher chance of rain and cold temps for a lower chance of mosquitoes. If you have to deal with them it will be mostly at the beginning of your trip. Once you get to September in the high Sierra they really aren’t a factor. I did the JMT from Lyell in 2020 8/16-9/2. Our biggest challenge was smoke from wildfires forcing us to push on past some planned campsites but we made it. I recommend a bag/quilt accurately rated below 30 degrees. Enjoy?!

John Girot

On Mar 12, 2024, at 10:42?AM, Jim Z via groups.io <jfz@...> wrote:

? There have been years where September in the Whitney area, especially late September, are _very_ cold. When I finished the JMT last week of September 2019, the last two/three days were below freezing, even during the day. Logistics, like keeping water liquid, can catch one by surprise. Another thing to remember about September is shorter days. The “Pickup at the Portal” episode in my podcast gives details of my experience. (I believe late September 2019 was anomalous as far as extremely cold weather in the Whitney area.)

?-Jim Z


 

Thank you Jim for the heads up. Will keep that in mind when planning. Hopefully we can finish it before 9/12 (22 days) or even 9/10(20 days) before it gets too cold.

On Tue, Mar 12, 2024 at 10:42 Jim Z via <jfz=[email protected]> wrote:
There have been years where September in the Whitney area, especially late September, are _very_ cold. When I finished the JMT last week of September 2019, the last two/three days were below freezing, even during the day. Logistics, like keeping water liquid, can catch one by surprise. Another thing to remember about September is shorter days. The “Pickup at the Portal” episode in my podcast gives details of my experience. (I believe late September 2019 was anomalous as far as extremely cold weather in the Whitney area.)

?-Jim Z


 

Thank you Johnny!
Yes, I usually take a 10F down sleeping bag and a R6 sleeping pad in my trips even in summer months.?
Forest fires have made my Sierra North ?Lake to South Lake trip cancelled twice?. Hope this time it won’t be?that bad.



On Tue, Mar 12, 2024 at 11:41 John Girot <johnnyg72@...> wrote:
Congratulations Jingbo! I think you’re going at the perfect time. I’m one who would gladly trade a higher chance of rain and cold temps for a lower chance of mosquitoes. If you have to deal with them it will be mostly at the beginning of your trip. Once you get to September in the high Sierra they really aren’t a factor. I did the JMT from Lyell in 2020 8/16-9/2. Our biggest challenge was smoke from wildfires forcing us to push on past some planned campsites but we made it. I recommend a bag/quilt accurately rated below 30 degrees. Enjoy?!

John Girot

On Mar 12, 2024, at 10:42?AM, Jim Z via <jfz=[email protected]> wrote:

? There have been years where September in the Whitney area, especially late September, are _very_ cold. When I finished the JMT last week of September 2019, the last two/three days were below freezing, even during the day. Logistics, like keeping water liquid, can catch one by surprise. Another thing to remember about September is shorter days. The “Pickup at the Portal” episode in my podcast gives details of my experience. (I believe late September 2019 was anomalous as far as extremely cold weather in the Whitney area.)

?-Jim Z


 

Early to mid September has been the most stable month for hiking in the Sierra for me. The remaining mosquitos are gone. But there's still plenty of water.

After Labor Day, the crowds are much diminished. It does get colder at night, but my 15F sleeping bag and 10F quilt have never left me cold.

Days are getting shorter but still plenty of daylight for all but the most ambitious mileage goals.

I've never gone later than September 20. As you get closer to October and into October the risk of a storm leaving significant snow increases. I would like to do an October hike at some point, maybe a briefer section to be able to forecast weather more accurately.?

 

Thank you Ravi, that’s very encouraging ?

On Thu, Mar 14, 2024 at 06:57 ravi_jmt2013 <ravi@...> wrote:
Early to mid September has been the most stable month for hiking in the Sierra for me. The remaining mosquitos are gone. But there's still plenty of water.

After Labor Day, the crowds are much diminished. It does get colder at night, but my 15F sleeping bag and 10F quilt have never left me cold.

Days are getting shorter but still plenty of daylight for all but the most ambitious mileage goals.

I've never gone later than September 20. As you get closer to October and into October the risk of a storm leaving significant snow increases. I would like to do an October hike at some point, maybe a briefer section to be able to forecast weather more accurately.?

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