I started a Snowball Earth Challenge playthrough and was unsatisfied with the existing mods that made surviving in a cold climate viable, so I made my own. I may make more changes as I figure out what I like and don't like (although world gen is likely to stay the same).

As of V1.2.0, all temperatures and other changes are configurable if you have Config lib installed. Otherwise the default values/settings will be used.

Changes include:

• Red, blue clay, and fire clay can now be found down to -25. In addition, red and blue clay now can spawn in barren soil (which is pretty much all there is at that temp).
• Cattails can now be found down to -18. They also now keep growing down to -4 and reset their growth timer at -9.
• Peat can now be found down to -25 and can spawn in barren soil.
• Horsetails can now be found down to -15.
• Bees can now be found down to -15.
• Salmon can now be found down to -15.
• Flax can now be found down to -2.
• Rare oak trees can be fround from 2 to -18 so leather can still be made. Be sure to get some saplings before you cut it down!
• Removed the min temp from traders.
• Flint deposits now generate in all types of stone, which causes loose flint to appear on the surface. Since loose stones don't generate on the surface at low temperatures, previously you needed to rely on flint deposits or finding rare stone spawns inside caves just to make your basic tools. And since flint used to only spawn in certain rock types, you probably needed to either travel long distances or just getting lucky with the rock type around spawn.
• Cranberries and blueberries spawn in small patches from -2 to -18, and have been changed to stop growing at -4, reset their growth timer at -9, and revert (go from fruiting/flowering to empty) at -14. This is to mimic bilberries and arctic cranberries which grow in cold climates IRL.
• Lakes (and rivers if you have a mod that adds them) now have muddy gravel as their bottom layer instead of plain gravel. This is mainly so I could still pan for seeds using Wild Farming.
• Mudbricks can be made out of barren soil. Not sure why this wasn't an option before.
• Seaweed can now be found down to -20. If the Inuit had seaweed in their diet, I think it's safe to say it can grow in cold sea waters. Not edible on its own but is with Long-Term Food and Expanded Food. It's also cultivatable with Wild Farming.
• Hornwort, muskgrass, milfoil, watercrowfoot, sea lace, irish moss, and bladderwrack can now be found down to -20, mainly to make lakes and oceans look a little less barren.
• If Salt and Sands is installed, scallops, clams, and freshwater mussels all spawn in small patches down to -18. They still grow at their regular temperatures (stopping at -6 and resetting at -8 for scallops, stopping at 2 and resetting at 4 for the others) so don't expect much mid-winter food from them!
• [1.1.0] Elk can now be found down to -18, which isn't much of a change from -14 but it means less distance to travel for a mount. And historically they were found pretty far north.