Your claim about northern cities is just not backed up by data, we have:

- the large amount of bike culture in Minneapolis, people ride all year long (once you're moving you'll stay pretty warm with the right gear) https://gearjunkie.com/biking/minneapolis-bike-capital

- the bike culture in Finland where it's even colder: https://www.theguardian.com/environment/bike-blog/2020/feb/0...

the difference in most of the US that it's not prioritized by local government, bike lanes don't get plowed and fill up with gravel, there's not sufficient bike infrastructure to being with etc

And for hot places: have a look at how Singapore deal with these things.

(Yes, it's too hot to enjoy biking during the day. But public transport is great, and has aircon.)

The Not Just Bikes Youtube channel did a great episode on why some places have winter cycling and others do not: https://www.youtube.com/watch?v=Uhx-26GfCBU

I think there are steps that could help reduce the affects of heat. Things such as more street trees, less asphalt (reduce the heat island effect), heat reflecting building roofs, etc.

It's not like the south is a lost cause, improvement can still be made.

Perhaps but 102 is still 102. I think you can make the same argument in Chicago when it's 10 and snowing.

Chicago can (and in some areas has - along with Boston) fixed that issue with pedestrian tunnels that allow easy movement during cold weather. A similar fix is available for southern cities but I think a more reasonable approach is just tighter pedestrian alleys that prevent full sun from ever bathing the walking surface (and reduce sun exposure to buildings) along with lots and lots of trees. Trees are seriously amazing and dissipating heat from the sun.

Once you eliminate the sun you just need to make sure that wind alleys are set up to keep air moving through the city and have regular green spaces with water to help reduce air temperature. This can be done quite sustainably - Las Vegas is actually a great example of (rather) sustainable water use from a city built in the middle of a desert.

Plenty of people walk to do things like get groceries in Chicago.

Heck, there is a subartic city in Finland with 12% cycling share, which is a lot higher than pretty much any city in North America. https://www.euronews.com/my-europe/amp/2021/01/22/meet-the-b...

I lived car-free in Chicago for 7 years. I now live in an inner-ring suburb (Oak Park), car-light (my wife and I share a car that I drive as little as possible). If we define 15 minutes as ¾ mile walking distance, I have within that range, two supermarkets, a library, health clubs, coffee shops, two drug stores, dry cleaners, banks, doctors, dentists, schools, daycare and a number of restaurants not to mention a stop on the “L” and at least half a dozen bus routes within my 15-minute zone. If I didn’t prefer Trader Joe’s to a mainstream super, I wouldn’t drive to go grocery shopping (and TJs is just over a mile away). If I expand my range a bit more, I add in even more of all the above plus a book store and movie theater.

Perhaps we shouldn't be encouraging people to live in such places then

Tell that to the Russians and the Spanish...