Cold Weather Test for Water Bottles

Cold Weather Test for Water Bottles

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Cold Weather Test for Water Bottles

Staying hydrated in the winter is very important. It is hard to drink frozen water! Here is a simple test of waterbottle done to simulate typical conditions in Colorado.

Cold Weather TestLeft to right: Walmart thermos, Nalgene bottle with OR insulating jacket, REI thermos.

Initial measured water temperature just before placement in the freezer was 69.8F. 850 ml of water was used for all items to prevent cracking of bottle during expansion.


The bottles were placed in the freezer at 8:07 PM October 11 2007. A digital high/low thermometer accurate to 0.1 degrees F was used to record the freezer temperature.

By morning it was found that the freezer temperature stayed between 3.5F and 7.2F throughout the night.


Average winter temperatures on Pike Peak are displayed in the following summary of the weather statistics:

Pikes Peak Weather Statistics

Of course it is often colder than average. Displayed below are some of the temperatures I have camped in the local area for each month of the year:

Overnight Temperatures in the Central (US) Rockies

It is evident that the recorded temperature of the freezer is fairly typical in temperature when compared with the weather statistics on the highest Colorado mountains.

The bottles were all removed from freezer at 7:22 AM on October 12 2007. This is 11 hours 15 minutes after their placement. As per my experience 10-14 hours is a typical time to climb in a day for winter ascents.



Nalgene bottle with OR insulating jacket

Notice that the Nalgene bottle (which was placed upside down in the freezer is frozen. It still did better than expected. Approximately 40% of the water in the bottle was frozen. The remaining portion of unfrozen water was at about 32F. Since I’ve had water freeze completely solid on climbs, it shows how cold those days were on those particular climbs.

Walmart thermos

This did surprisingly well. I have actually had water turn slushy in it on very cold days, but for this test the water stayed well above freezing. The measured temperature at the end of the test was 42.4F, well above the freezing threshold.


REI thermos

This is the best performer. I have never had water freeze while using this product. For this test the measured temperature at the end of the test was 50.2F, well above freezing.



For cold winter climbs, do not rely solely on Nalgene bottles and insulating jackets unless you have them close to your body the entire time. At a minimum, take at least one high quality thermos (such as the REI one) to make sure you have water available after the Nalgene bottle freezes.


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Viewing: 1-20 of 33

nader - Oct 12, 2007 2:09 pm - Voted 10/10


I don't do any winter climbing but this was a very interesting home experiment.

Anya Jingle

Anya Jingle - Oct 12, 2007 9:26 pm - Voted 10/10

I agree with Nader

Thanks for putting the effort for this interesting experiment. I have tried various thermoses, but REI one has been my favorite. There is nothing like a hot apple cider on a cold winter summit!


CookieMonster - Oct 12, 2007 11:57 pm - Voted 10/10

Could also add agitation

Try agitating the water a little - like what would happen while you are walking. This will help the water to freeze, especially if it's very pure (i.e. filtered water) because the water needs some impurities to start growing an ice crystal. With pure water, you might find it well below 32F and not frozen until you shake it! Nice experiment.

Dan Dalton

Dan Dalton - Oct 14, 2007 2:03 pm - Hasn't voted

Reminds me of a middle school...

science fair project. Really cool and unefull information Scott. Great idea.



Andino - Oct 15, 2007 10:06 am - Hasn't voted

Also interesting...

is to see the pipe of a camelbak freezing and getting useless, below 0°C.


itpimps - Oct 17, 2007 2:11 pm - Voted 10/10

Re: Also interesting...

I agree, my insulated camelbak tube has helped to keep water cool in summer as well as freezing in winter, but it has frozen over many times while I ski. I've found one of the best ways to prevent freezing in the tubes was to blow all the water back into the bladder because the water within the tube was an easier target for freezing. I'd love to see an article comparing the various bladder tube assemblies and the "insulation".

Great read-I'll have to checkout the REI insulated thermos...


Saintgrizzly - Oct 17, 2007 2:32 pm - Voted 10/10

Very worthwhile page...

...I see an REI purchase in the near future! Sometimes, I've even taken a stove just to melt snow—obviously cumbersome and time-consuming! Thanks for making the effort on this, Scott!


zenalpinist - Oct 17, 2007 3:52 pm - Hasn't voted

Another thing to note... that as you drink water from said bottle/thermos, the volume decreases and becomes more able to freeze. From pure field observations (not scientifically setup) I have inserted two nalgenes into identical OR sleeves with warm water, one full and the other a bit less than half full. After several hours of skiing around, the bottle with less water has begun to slush-up and freeze, while the full bottle is still warm.

So keep that in mind as water gets drunk from the bottle, the system is changing. On some very cold days I've had the bottom 10oz or so freeze solid and I just have to switch to another bottle.


itpimps - Oct 17, 2007 4:10 pm - Voted 10/10

Re: Another thing to note...

Great point!


jvarholak - Oct 17, 2007 6:52 pm - Hasn't voted

great info...

thanks for your work....can you post the weights of each bottle tested?...or...i guess i can stop being lazy and look them up myself :)

Trevor Simmons

Trevor Simmons - Oct 17, 2007 10:14 pm - Hasn't voted

thanks Scott

Valuable experiment for all of us that venture out in the cold months...


Josh_Inked - Oct 18, 2007 1:03 am - Voted 10/10


Thanks for the experiment. It is one more valuable tidbit to take into acount.

Boriss Andean

Boriss Andean - Oct 18, 2007 1:27 am - Voted 10/10

Very useful information...

Thanks for posting this article Scott.


baloodh2000 - Oct 18, 2007 10:11 am - Hasn't voted

Good Info

Thakns for the home experiment. Gearing up for my first winter mountaineering season. Really usefull!


Smith93 - Oct 18, 2007 1:49 pm - Hasn't voted

And the winner is...

Awesome! I'm excited that the REI thermos performed so well. I'll have to remember that the next time I'm at work.


Snowpuppy - Oct 19, 2007 9:07 am - Hasn't voted

Very Intersting

Way cool, now I can pull my thermos out of storage!!


dpk - Oct 19, 2007 9:17 pm - Voted 10/10

dont drop your bottle

Also as a note - frozen nalgene bottles can shatter if dropped on large rock from slight distance - but thats about the only time a Nalgene will break
Good stuff here - I also use a thermos as well


gomez13 - Oct 20, 2007 10:32 am - Hasn't voted

nice experiment

Good beta I just had two nalgene bottles freeze solid on me on Mt Langley a couple weeks ago. the REI thermos seems like the way to go


BigLee - Oct 20, 2007 5:07 pm - Hasn't voted


Do you work for REI? What do you reckon the difference between the two thermos is due to?


Scott - Oct 20, 2007 5:21 pm - Hasn't voted

Re: Interesting

Do you work for REI?

Nope. Actually I just threw this experiment together to answer a question on the forum. I disagreed that Nalgene jackets are always adequate for winter climbs in this area and since I already wrote it all up, I thought I'd copy my forum post over there as an article over here as well. Here's the thread and my first post if you want to read it:


The same article here is the forum post at the beginning of page 3.

What do you reckon the difference between the two thermos is due to?

The REI one is definately better built. On the other hand, it's also almost 3 times more expensive, so it should be better built. The Walmart thermos is probably more meant for taking hot beverages to work or maybe the ski slopes; the REI for the outdoors. I'm actually surprised the Walmart thermos did so well. I still wouldn't want to drop it too many times, but it is still better than just a Nalgene with a jacket.

Viewing: 1-20 of 33