Modify world temperature - sorta worked, now it doesn't. Help?

A few weeks ago I had a blast surviving a really harsh winter. Average temps were in the -40C range. I had to be careful to bundle up and remember carry proper bedding, find shelter and so on. A mistake invited pain and damage and death. Fun!

Got there from a tip on Reddit about changing regional_map_settings “base_temperature”

But it seems to have stopped working. No matter how low I set it now the New England winter remains fairly mild.

Any advice to restore my brutality level?

I am going to take a stab in the dark here, since I am not familiar with rules on temperature.

I THINK base temperature for the map is set when the map tile is created, and regional_map_settings “base_temperature” only adjusts it but only during creation.

Therefore, only new map/tiles you discover will have the said changes applied to. My advice is to go to the new tile and see if temperature change applies?

Worth a shot. I seem to recall teleporting around to a whole different region with no effect, but I was goofing off rather than doing SCIENCE. Will test.

Set to -26.5 (default is 6.5)
Load a game. Walk about on the surface. Winter, day 77, -3C.
Teleport to far off places. And then again so far I have no map of them. Walk around a bit. Still -3C.

Start a new world, no mods, new character.
Walk around a bit. Yikes! -31C.

OK, that tells me something.

Whelp. Shoot. OK, can’t change it in an ongoing game and it doesn’t seems to change underground temp. Still 6C downstairs when it is -31C on the surface.

I was hoping for a long-term climate wildness approach, harsh winters and broiling summers. Maybe one day.