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PUNKINPUSS11
01-15-2010, 13:05
im reading alot of conflicting reports on the temp on the JMT in august. Some say 70 in the day and 50 at night some say hail and snow??? can anyone clarify average temps or does it vary that much??

Miner
01-15-2010, 14:23
Snow isn't normal, but it does happen in summer (I've seen it in summer). Hail certainly does due to the big thunderstorms that often develope. If you encounter hard rain from one, the temperature does drop and you don't want to be hiking along in just shorts and a t-shirt if it last for very long. You are in high alpine country which means unpredictable weather. So its best to be prepared for it.

When I backpack in the Sierra Neveda in summer, I always bring a lightweight baselayer, an insulating upper layer, and a rain jacket. I often don't need it all, but there are times when I do. You should be prepared to handle everything from low 80's to freezing temperatures.

Dogwood
01-15-2010, 18:37
Just some educated guessing, but I would say the temp swing can be even greater than the highs/lows you list. In Aug you could experience highs in the high 70's for sure, maybe even 80's. Lows can be as low as freezing with avg lows, I would think lower than 50*, maybe in the 40's. I'm kind of saying what Miner said. - You should be prepared to handle everything from low 80's to freezing temperatures. - Miner

To me, a lot of this, in Aug, is largely dependent on elev, and exposure. That's why when I research avg high/lows for any of my hikes I'm very careful to note for what elev and where exactly those avgs are taken from. Can be very different weather on the rim of the Grand Canyon compared to the bottom of it at the Colorado River. Can be very different weather on the north and south rims even though they are less than 12 miles apart as the crow flies. Likewise, can be very diffrent weather at Mt Whitney summit and Yosemite Valley! I think you get my pt?

It can snow/hail in the Sierras any month of the yr. In Aug be prepared for an afernoon thundershower of usually short duration, like an hr. I would go w/ a light wt wind/rain jacket. I've hiked the Sierras in Aug when I carried it and did not need it, but there were times I was glad I had it. I've NEVER experienced an all day rain in the Sierras.

On the JMT in Aug bring sunscreen(intense rays) and sunglasses. Most thru-hikers will get away w/ a 35 * sleeping bag. Be ready w/ those layers like Miner said. I'll quote him again - When I backpack in the Sierra Neveda in summer, I always bring a lightweight baselayer, an insulating upper layer, and a rain jacket. I often don't need it all, but there are times when I do. - Miner

Now, here's more good news. The Sierras/JMT, especially during Aug, and for its elevation, has some of the most temperate weather of any major mountain range in the U.S., maybe the world. Fine time to be on the JMT, but more people of course!

Helmuth.Fishmonger
01-19-2010, 11:37
depends on elevation and weather.

If things go well, expect 80s as a high below 9000 feet for sure, 50s at night. Higher up, subtract 10 degrees each 1500 feet.

Get a bad storm, you are down to 50 down low, hail and 30s higher up. At night, it freezes above 10500 feet unless you are in a really hot stretch.

Rambler
01-20-2010, 15:21
Note what my daughter was wearing in the AM getting ready to hike,(Tuolumne Campground... then note what she was wearing a couple hours later (Lyell Valley)

tothetrail
04-04-2010, 13:42
Note what my daughter was wearing in the AM getting ready to hike,(Tuolumne Campground... then note what she was wearing a couple hours later (Lyell Valley)

Wow, it looks like it warmed up fast!

tothetrail
04-04-2010, 13:42
And thanks for the pics, it really helps to get a visual!