The 4 Seasons:
With inspiration from Don't Starve, the seasons are recreated and will cycle naturally every 20 days (which makes for a 80 days year), each with their own specificity:

• Autumn/Fall: The most calm season of the four. Nothing special really happens to give you time to prepare for the next ones. Leaves fall from trees, the temperature only gets a little cold during the night, and no real change to the environment happens. Rain may start to fall, but you can protect yourself from it with a leather helmet.​
• Winter: The cold season, and the first one where there is a threat to your health: the temperature drops low enough for you to feel the effects, and even more during the night. Snow is constantly falling, covering the world in a nice white coat, as water freezes and small flowers disappear to protect themselves. Skeletons outside of caves will become a rare sight as they will be replaced by Strays under the effect of the cold. All crops will stop to grow due to the rough conditions. A blizzard may start causing snow to pile up, so beware of that for the duration of the season!​
• Spring: Another quite calm season. The temperature is a little high and may lead you to be careful while transporting flammable items in your inventory. Rain will fall more often, as well as thunderstorms will happen for the first time, and flowers will bloom back out where the sunlight can touch a patch of grass. And flowers won't be the only ones to bloom, as everything will grow in average twice as fast during this season compared to Autumn!​
• Summer: The other extreme season, this time with the heat, but still with a threat to your health if you are not careful. The heat will stay during the night, although not as prominent. Zombies outside of caves will transform into Husks under the heat. Heatwaves may happen, where the temperature skyrockets once again and the grass starts to smolder back to dirt, that may even become sterile. Wildfires will appear but will hopefully be put out by the important thunderstorm that follows, during which lightning will strike quite often, before returning to the usual clear weather.​

Temperature and Wetness:
Two new mechanics have been added with this datapack: temperature and wetness.

• Temperature: It is what you expect. Keep it around the green and everything will be fine. The UI will show you your current feeling of temperature (rather coarse) as well as your feeling of heat (the change of temperature, again rather coarse). Hiding in a cave (below y = 40) will protect you from the ambient heat that changes with the seasons, but only in the Overworld.
• Wetness: It's quite a side mechanic. It will increase as you expect, while standing under rain without protection or staying underwater too long. It will cool you down quite fast if you're not careful, and may even result in having your tools slip out of your own hands.

Dimensions:
Of course, the other dimensions aren't set aside. They are not affected by seasons, but that doesn't mean they have their own quirks.

• The Nether: It's really hot in there. So hot in fact that your temperature will increase around twice as fast as in the Overworld, and that's ignoring the melting pools of lava and pockets of glowstone and magma blocks everywhere. Better bring some ice with you if you don't want to be burned to a crisp by just standing there. Be also wary that the extreme heat can also pass through the portal.
• The End: Pretty much the same deal, except it's really cold. The void isn't forgiving and will turn you to ice while fighting the Dragon if you do not pay attention to your feeling. And again, this extreme cold can pass through the portal.

Side Notes:
A huge thanks again to the Phoenix SC and Datapack Center communities who gave me ideas to add to this project. Feel free to send me feedback on how I could improve this project or for new ideas to add.

• This Datapack is in theory multiplayer-compatible, although no testing has been realized to ensure either the functionality or the performance. The MSPT (ms per tick, the time it takes for the game to calculate a game tick, should generally be under 50 ms for 20 ticks a second) was increased by 10 to 15 ms during testing and optimization is again a top priority.
• There is a lot to this datapack: interactions with items, armors, blocks, mechanics, etc... and it's all up to you to discover them! If you want to, I'll add a list of all interactions currently in the project on a separate file for those who like to know how everything works exactly.
• There is now an option menu: to access it, simply run the /function seasons:options command. Don't forget to click [​Done] once you are finished!
• IMPORTANT NOTE: There are also Advanced Options allowing you to enable/disable pretty much everything there is in this pack. If you just want some part of it, then there's most likely an option right for that.

Download Link:
You may have noticed that the download link redirects to The Datapack Center. The reason why I did this is because it allows me to update both of these sites at the same time, and because I find the update system there better.