I have never felt it, so what do you mean by extremes? I do not think a daily commute for 50 minutes in -15°C at ~25km/h on a bicycle is extreme. I never feel affected. I also go Nordic sking in -30°C for hours I have never been affected. The sun with snow blindness is not fun though never doing that mistake again.
I suspect this is one of those cases where people who don't live in cold climates overestimate how rough it is. I also live somewhere where -30C is not rare and it's perfectly normal to spend hours outside in that weather. You just layer up, but outside of mountain skiing I don't think I've ever worn goggles.
I also live in a cold climate. I get very bad eye problems below -15 C. at -10 I can handle just using my normal glasses but below -15 I need goggles. At -20 I put on a balaclava with goggles on top. It all depends on your age and medical problems.
The temperature problem can also be underestimated. You really need the right clothes. I have a little list on my phone for what to wear at what temperature and I pack some alternative clothes to add if needed. In case wind was harder than anticipated or it's so slippery and bumpy that you will never get any sort of speed.
I use Lungplus for breathing. I have two models, one for below +10 C and one for below 0 C that heats better. Asthma isn't funny. Cold allergy neither. I'm probably not totally sane going biking at -35 C.
I was out the other day cycling in -13°C, and I was the perfect temperature, didn't sweat, wasn't cold. The next day it was still -13°C, so I wore the same clothes, but I was cold, my fingers and toes went numb, and I ended up cutting the ride short. The difference between those two -13°C days was the humidity. It`s huge!
I can only imagine what it's like living somewhere actually cold. I've got pretty bad asthma (severe enough that I'm on a maintenance med on top of the rescue inhaler) and allergies. Cold is a big trigger for my asthma, and yea, after doing the conversion 10C is about when I'd start to really notice, but I probably start seeing some effects around 15C or so. Luckily I live in a temperate area, the coldest it ever gets is about -5 or so. My other big asthma triggers are exercise and my allergens - which are all the basic boring stuff - pollen, ragweed, mold, dust, etc. So basically walking outside is like getting punched in the lungs. I started wearing N95 masks basically when I was able to get my hands on them (so, early 2021) and eventually settled on the 3M Aura actually mentioned in another post. They really do warm the air quite a bit, enough to mostly not trigger my asthma, and help a lot with the allergies too. I've also only gotten sick once in 4 years, and that was last year when I took my mom out for a mother's day meal at a packed restaurant. I really try to avoid restaurants during peak hours. Ironically strep and not COVID. So, basically, starting wearing them for one health reason, have kept wearing them for that and for several side benefits that were happy discoveries.
I have to be really careful as I have a number of other chronic conditions, including diabetes, and between them, and the meds I take for 'em, I'm usually rather fatigued and run down at the best of times. It's quasi-stable, but I've been hospitalized several times foe respiratory issues, and I'm only in my 30s, and to be frank, none of what I have exactly gets better with age.
I'm sorry to hear that, I can only too well imagine how it's like. I'm just like you but several notches better and 20 years older and no diabetes. It helped a lot to start biking and I'm getting better and better thanks to the lungplus. But I do feel like I got hit in the lungs now and then if I don't start very slowly. After 15-20 minutes I can start with uphill and higher speeds and all feels fine again.
It's a really vicious cycle. Right before the pandemic, I had a decent routine up, was down about 40lbs.. still big, shut down...then the pandemic, everything shut down (including my gym, permanently). About a year later for no real reason any doctor has been able to really explain beyond "well, you're diabetic and have unfortunate bone structure" I developed pressure ulcers on the bottom of both feet nearly simultaneously, in roughly the same (mirror imaged) spot. The second broke out just as the first was starting to heal in earnest. Basically spent June 2022-March 2023 on near bed-rest as that was the only way to actually get them to heal. They've both since healed, but my feet are never really gonna be the same again, plus there's nerve damage etc that basically means I don't have a ton of sensation down there anymore. Which is a long way of saying... you know how in TV commercials for gyms and the like it always says "consult your doctor before starting any exercise routine"... that's my actual life.