So I was flying in -20C again, knowing that's too cold for what the Mini2 is rated, but it's been done before with little or no issues by others.
Anyways, the drone at some point just started climbing on its own again, but it was close to home and I fought it back down till it landed safely.
Here's my flightlog:

https://www.phantomhelp.com/LogViewer/NVZXKO7JI6SNJDRA43G1

I've flown in warmer weather, but still in the ~-15C without issues.

I'm just curious if anyone else out there as experienced anything like this.

Hello there Snoopy70. I am sorry for the trouble this has caused and thank you for reaching out. Just a reminder that the DJI Mini 2 has an Operating Temperature of 0° to 40°C ( 32° to 104°F ). Thank you.

Are you going to fly this in the cold again, if so and you get a repition of this uncommanded climb  could yo try reducing the maximum height setting in the app to below its current height? I think it should force the drone down.

I would like to know what are the limitations of the drone that determine that it can only operate above 0ºC?
Look at the perfect example below. 2 near identical aircraft, yet the older model can hit -10ºC, what gives?
Why can it do that and not the 2s, what determines what temps an ac get fly in?
Why is the Phantom 4 Pro has the same limitation as the Mini 2 when it comes to operating temps?

Air 2   Operating Temperature Range -10° to 40°C (14° to 104°F)
Air 2s Operating Temperature Range    0° to 40°C (32° to 104°F)

Bashy Posted at 1-23 22:30
I would like to know what are the limitations of the drone that determine that it can only operate above 0ºC?
Look at the perfect example below. 2 near identical aircraft, yet the older model can hit -10ºC, what gives?
Why can it do that and not the 2s, what determines what temps an ac get fly in?

Could be as simple as a change of component to save some $$$ and that components data sheet doesn't go as low as -10c.   Very few will ever fly that cold so by saving some $$$ they wont effect sales that much.

It looks like it detected a battery issue and initiated an auto RTH,  my guess is that it was climbing to your RTH height.

Do you happen to have the subtitles on at the dji fly app?
If you do, what does the Vs read when drone was gaining altitude?  

I have seen a few instances where the Vertical speed reads negative when the drone is climbing up.
I had similar thing happen to my drone and also in cold weather.
My wild guess is that the barometer or accelerometer don't like cold weather.

DAFlys Posted at 1-24 02:08
It looks like it detected a battery issue and initiated an auto RTH,  my guess is that it was climbing to your RTH height.

After noticing the unwanted/uncontrolled climbing, I returned to home on my own, fighting the climbing on and off. (I’m not sure the joysticks are showing all this, but my video does).
At one point I did initiate the rth, but cancelled when I wasn’t sure if I was surpassing my rth height, just wanted the drone back home safely.
I’ve flown recently in warmer weather, but seems this really cold weather affects the drone AFTER several minutes of good flying.
I know there’s been others flying in these extreme cold weather, just curious what they’re experiences are.
Also is it the battery, or the drone causing this.
Thanks to all for your inputs, good or bad.

Bashy Posted at 1-23 22:30
I would like to know what are the limitations of the drone that determine that it can only operate above 0ºC?
Look at the perfect example below. 2 near identical aircraft, yet the older model can hit -10ºC, what gives?
Why can it do that and not the 2s, what determines what temps an ac get fly in?

Limitations are mostly related to battery performance and gimbal. DJI drones use certain rubber in gimbals that gets really stiff when cold and then gimbal starts to shake, like so:

https://www.youtu be.com/watch?v=tQvEhy21Jmk&t=967s

Sakari Kaulaote Posted at 1-24 03:43
Do you happen to have the subtitles on at the dji fly app?
If you do, what does the Vs read when drone was gaining altitude?  

Sakari, I’m not sure how to get the subtitles on the fly app. I posted my flight log in case someone wanted a better look at what was going on, including the battery fluctuations.
I posted this problem earlier, and it was the same battery (they’re numbered, so I know), and I’m going to chance trying this again with a different battery, just to see.

I should also mention I’m on flyapp 1.4.8.(1185), if that makes any difference.

To me it looks like battery issues probably caused by the extreme cold.   You also are on a very old version of the app no reason not to update that.

DAFlys Posted at 1-24 02:07
Could be as simple as a change of component to save some $$$ and that components data sheet doesn't go as low as -10c.   Very few will ever fly that cold so by saving some $$$ they wont effect sales that much.

Yeah, that makes sense, me, i would prefer the -10C any day, but i also like the extras the 2s has over the 2. To be honest, come winter time, the best scenery is when its colder and many fly sub 0 that's for sure, perhaps not as many <-5C, so that saving DJI make is poop for the consumer if that is the reasoning mind.

Bashy Posted at 1-25 00:00
Yeah, that makes sense, me, i would prefer the -10C any day, but i also like the extras the 2s has over the 2. To be honest, come winter time, the best scenery is when its colder and many fly sub 0 that's for sure, perhaps not as many

It happens all the time in manufacturing,  they find cheaper parts and then work out how much they will save vs how much they would loose in sales,  if any.

DAFlys Posted at 1-25 00:17
It happens all the time in manufacturing,  they find cheaper parts and then work out how much they will save vs how much they would loose in sales,  if any.

Yeah, i can also see them with that attitude with regards to warranty too, many of is fly in sub zero during the winter, but if they state a minimum of 0C then there is no liability on DJI's part, so they have basically limited the amount of warranty claims right off the bat...

I'm just curious if anyone else out there as experienced anything like this.
Yes .. and the data showed that the altitude sensors and altitude stability are unreliable when flown in very cold conditions.
Also you started with a partially discharged battery which meant the battery had less charge than the % indication showed.
The battery issue was responsible for multiple warnings that said:
Battery power restricted. Aircraft performance decreased to ensure flight safety. Return to home promptly.
But a low battery does not cause uncommanded climbing.

DAFlys Posted at 1-24 02:08
It looks like it detected a battery issue and initiated an auto RTH,  my guess is that it was climbing to your RTH height.

my guess is that it was climbing to your RTH height.

The RTH height was set to (60 metres), so the drone wasn't climbing to RTH height at all.
Why guess when it's very easy to check details in the recorded flight data.

Labroides Posted at 1-25 05:44
my guess is that it was climbing to your RTH height.

The RTH height was set to (60 metres), so the drone wasn't climbing to RTH height at all.

Not sure were youre seeing that its not on the website he linked to.

Labroides Posted at 1-25 05:44
my guess is that it was climbing to your RTH height.

The RTH height was set to (60 metres), so the drone wasn't climbing to RTH height at all.

PS Whats wrong with being nice and pointing to actual information and educating people rather than your constant criticism.

DAFlys Posted at 1-25 05:50
PS Whats wrong with being nice and pointing to actual information and educating people rather than your constant criticism.

PS Whats wrong with being nice and pointing to actual information and educating people rather than your constant criticism.
That's what I did.
I pointed to the actual information and attempted to educate a little.

Labroides Posted at 1-25 06:14
PS Whats wrong with being nice and pointing to actual information and educating people rather than your constant criticism.
That's what I did.
I pointed to the actual information and attempted to educate a little.

You made a statement, you didnt show where that information came from.

DAFlys Posted at 1-25 06:28
You made a statement, you didnt show where that information came from.

I pointed out that it was in the recorded flight data .
What more do you want?

Labroides Posted at 1-25 06:41
I pointed out that it was in the recorded flight data .
What more do you want?

Its not on the phantom view log he posted a link to.

Labroides Posted at 1-25 05:44
my guess is that it was climbing to your RTH height.

The RTH height was set to (60 metres), so the drone wasn't climbing to RTH height at all.

Was too lazy ,in a hurry to post I guess.
Thanks to all who help me here (wether you’re nice about it or not, I can take it.)
Anyways, I’m just curious about how my beloved drone reacts, what others have experienced . Ya, I’m taking chances, but I ain’t waiting till spring to fly this thing if I can help it.  I do have DJI Care, but hope not to use it.

Be aware you need the drone if you are going to use care refresh, lose the drone into deep water etc. and you and it are probably 'sunk'.

DAFlys Posted at 1-25 07:12
Its not on the phantom view log he posted a link to.

Its not on the phantom view log he posted a link to.
If it isn't, then where did I find it?

Labroides Posted at 1-25 14:26
Its not on the phantom view log he posted a link to. If it isn't, then where did I find it?

I think what DAFlys means is that it is not directly visible on the processed results page, you have to download and open the csv to find the set RTH height in column EC / 133.

Sean-bumble-bee Posted at 1-25 14:51
I think what DAFlys means is that it is not directly visible on the processed results page, you have to download and open the csv to find the set RTH height in column EC / 133.

Thanks Sean,   thats exactly what I was trying to find out.