How cold can it get in the high sierras?

Justin, you need to supply a bit more information. Are you talking about summer only?

For July-August, let's say, and for Sequoia-Kings Canyon, and 9000 feet, nearly all of the time (95%) it will stay above freezing. What are you going to do for the other 5%? For 13,000 feet, that is kind of a different story. Assume that the temperature drops 3 degrees F per thousand feet of gain. You do the math. It can easily get down to 20 degrees F or worse. Easily. Plus at 13,000 feet you will have some more wind.

A friend of mine reports a time that he was at Wallace Creek one August when the temperature outside his tent got down to 10 degrees F.

Think about it. You have time to adjust.

–B.G.–

-15 F is the coldest I've seen in winter.

In summer I generally suggest that you equip to be comfortable at freezing; that should let you survive at 10F. With older overly optimistic temp ratings on sleeping bags it means a 15 or 20 F rating. 0 C / 32 F EN Comfort rating
Is likely fine without adding extra clothes.

Usually it doesn't go from nights in the 30's to single digits without warning. You will have time to hike lower as weather moves in.

Sorry, I meant summer. I am planning a trip out of mineral king in SEKI.
Maybe this is a good reason to avoid being above the treeline as much as possible in case of extreme temperature drops. I have been in that situation more than a couple times and a fire helped me get a decent night sleep, despite bodies of water freezing over all around me more than an inch thick.
Are there any specific factors that would help you predict an extreme temperature drop?
Also, would early june be colder than july and august?

A cold front can change things in a hurry, if it snows, it will get cold after the storm clears. Last summer in early August, I had temps from around 28F to a little above freezing my whole trip from first night at Vidette Meadow, Forester Pass, Colby Pass, Bubbs Creek back out Kearsarge Pass. Some will take a 20F bag and use their clothes to make up any difference. I only use a WM Caribou bag rated at 35F.
Duane

Justin, if you are really good, you can study the weather for a couple of days before you start, so you can get a better idea for action. For example, if you see that there is a cold front approaching, then alter your route plan to stay lower in the trees, and not so much up on Black Rock Pass. Carry 40% additional fuel. If worst case weather hits, you stay up all night long tending your stove and boiling water to put in a water bottle inside your sleeping bag every few hours. It's not elegant, but it will keep you alive. In my car, I generally keep one extra top and bottom warm layer. At the last minute before I leave the trailhead, I can pop that in the pack if I am really worried.

If you can stay absolutely 100% dry, you can stay warm. As soon as you get your only clothing wet, you are doomed to an ugly situation.

–B.G.–

I haven't spent the night at 13,000 but I've been many summer nights at 8,000-11,000. You often get frost in a water bowl or puddle on a clear night any summer month. So 35F is to be expected. A cold front, then no wind and a clear night and you could have 25F at 10,000'.

An incredibly useful bit of thermodynamic data is that when air expands, it loses 3.5F for every 1000 feet of elevation rise*. A high of 100F in Fresno means 100-(4×3.5) = 86F in Yosemite Valley at 4,000'. Afternoon high on Half Dome at 9,000' = 100 – (9×3.5) = 69F. If there's any air movement, this is accurate to within just a few degrees.

So extrapolating from my 10,000 foot experience, subtract 10F for 13,000 feet. Expect 25F, be prepared for 15F. The bigger issue is you could have 30F but 50 mph at 13,000 feet. Plus rain or hail. That's a tougher survival situation.

Be ready to change your plans, especially if you're going light. You can sometimes drop 5,000 feet in 2-3 hours, increase 17F, get out of the wind and into the shelter of trees.

*This is referred to as adiabetic expansion. Because of humidity, rainfall and increased solar input, while I use 3.5F/1000' on the upwind side (western side of the Sierra), the air increases 5F/1000' going down the other side.

CDEC maintains historical weather data for a number of weather stations throughout the Sierra, which include daily highs and overnight lows. You can find weather stations here: http://cdec.water.ca.gov/cgi-progs/staSearch

When I was preparing for the SHR last year, I compiled data for the last 5-6 years from all of the available weather stations over 8,000' between Sequoia and Yosemite for the months of August and September. The 2-sigma (95th percentile) overnight low for September was 25F. So if you were prepared for 25F, you would only be cold on average 1 night out of 20. If people are interested I can try to post up the data tomorrow.

I would guess for the middle of the summer you could add about 5F to that number, and if you plan on camping at lower elevations you could probably add another 5F. I would recommend looking at a few CDEC weather stations to get a feel for what to expect.

Andrew

If it's going to get that cold, I will definitley try and get into some tree cover and blast a fire in my face in the worst case scenario. I have done that down to the teens in my 35 degree bag with quite limited wood and I was fine, not warm though.
Just thinking bushcrafty and survivaly for a worst case scenario. Once I get past sawtooth I will be in the trees.

That's great info David! I will try and remember that.
It's sounding like a 20 degree down bag is in order… I have a well worn cat's meow but it's not the lightest or most compact, and probably isn't truly 20 degrees.

Andrew, maybe you are better at mining that weather data than I am.

I found one weather station on the ground just below Bishop Pass (near 12,000') and I assumed that it was typical of nearby places that I would find myself. I just use that one station's snow depth and temperature data for the whole range. It's not so accurate, but it is quicker to look over when I am only looking for a trend.

That station has a radio transmitter for the telemetry data, and the antenna has one element broken off the front. So, when I look at the data from home, I have that mental image of the broken antenna.

–B.G.–

"blast a fire in my face"

Justin, I think you know this. For many of those places, there are no wood fires allowed. Now, if you got into a true survival situation, I guess you have to do whatever you can do. However, a passing ranger might not take too kindly, and you would have some 'spainin' to do. Besides, there is not much wood up high in the first place. That's why I suggested the 40% extra fuel for your stove. That would be one situation when a nice white gas stove would feel great, or at least a good canister stove. Alcohol and Esbit work fine in mild weather.

–B.G.–

Bob, I remember being surprised that the Bishop Pass station was warmer than other locations, given that it's at 12,000'. Charlotte Lake was consistently the coldest. Not sure if it's actually colder there, or if the weather station is in the shade all day, or poorly calibrated. Sometimes the CDEC data is hit or miss.

Justin, if your system is warm down to freezing I think you should be fine. My data is for September when it starts to get colder. In the summer, most nights will be in the low 40's to upper 30's. It's probably not worth buying a new bag if yours is actually good to 35F… lots of people use 32F bags in the summer and are fine.

It is legal, in some of the places. At least below 10,400 feet in the big 5 lakes area. I wouldn't ever do that unless it got dangerously cold, like into the teens knowing how small the wood supply is and how delicate the ecosystems are. If it was just the mid 20's I would tough it out.
Do you mean using the stove to keep warm? Or using it to heat water?

If it ends up being colder than you anticipated, it doesn't have to be a big deal. Here are some tips to make your night warmer:

-Eat a snack before you go to bed so your body has calories to burn
-Put on ALL your clothing, including rain coat, extra socks, etc.
-Heat up a hot water bottle and put it in your sleeping bag
-Put all your spare items underneath your sleeping pad, i.e. backpack, maps, trash bag liner, etc. to give you extra insulation from the ground
-Pitch your shelter to the ground and close any doors to trap heat in
-Breathe into your sleeping bag so that the air you are breathing is pre-heated. While this isn't a good practice in general because it will eventually wet out the bag near your face, you can get away with it for a night or two and it makes you a lot warmer
-Cuddle with your neighbor if you've got one
-Do some jumping jacks before you get in your bag
-If you do end up shivering through the night, doing 30-40 situps when you get cold will warm you up, at least for a little while

I have spent a few nights out where I had really inadequate insulation, and while it's not much fun and you don't get a whole lot of sleep, you will be fine and will have a story to tell when you get back.

"using it to heat water"

If you heat water on your stove, you can use it as a hot water bottle inside your sleeping bag, you can drink it, and you can use it to make hot food. Not that much heat will be totally lost. If you just stand around warming your hands over a stove flame, most of the heat is lost.

Yes, lots of backpackers will study their camp elevation very carefully in some of those areas, and they will attempt to camp just below the limit. That way, they can have a legal fire if they need it. However, it is a good idea not to touch the wood at all unless you really, really need it.

I've seen too many backpackers building huge bonfires on a warm evening. They just burn up the wood because they think it's fun.

–B.G.–