Go to Markarth in the fall for a slice of mutton, visit Windhelm in the winter for a snowberry tart, go to Rorikstead for a fresh wheel of cheese... You get the idea.

• Vegetables and fruit is more rare in the winter, and dried/cured meat is more common than freshly cooked.
• The fall is where it's at for most vegetables, as well as a lot of meats - to have less chickens to feed in the coming winter.
• Spring is a safer time for most hunters (they stay away from cats though), as well as a good time for farmers to gather milk and eggs.
• Summer has some specific crops ready to be sold, and honey is common.
  

Granted that there is always a small chance to find some leftovers from the previous season, and some items are pretty common year-round.

Hold capitals are more likely to have more food, more elaborate food, and even rare drinks.

Villages have some regional specificity depending on their location too.

While the goal isn't to starve anyone, finding food in the winter should be a bit more difficult, especially in small villages.

Compatibility notes

MUST be loaded after EVERY other CACO dependent mod/patch.

Because it changes container and leveled list records, removing=rearranging default and/or added items.

Mods editing food merchants' inventory (such as MerchantMarkarthSilverFishInnChest, etc) would require a patch.
Mods editing leveled lists (such as LItemFoodInnCommon, etc) would require a patch.

Mods adding new inns/merchants will most likely have the seasonal loot automatically, but without regional additions.
For example, Old Hroldan offers juniper berry crostatas in the fall, but if you add an inn in Karthwasten, it won't do that by default, that would require a patch.
However as long as the new inn uses vanilla leveled lists for food (most mods do), common food will be seasonal even without an extra patch.

Load Seasonal Foods AFTER Interesting NPCs, MihailMods' Rustic Weapons, Trade and Barter, Requiem, etc.

Consult SSEEdit for further compatibility information.

You can request patches, but I can not in all honesty guarantee every request granted. Hopefully you understand.

If it a small mod, I am more likely to patch it. If it a massive mod, and I am not using it myself, I probably won't be patching it.

You can make a patch yourself, simply make it depend on this plugin (and the mod you're aiming to patch).

Patches

Last Seed patch: rebalances pickles and salted preserves, adds them to fall and winter loot.

Cheesemod for EVERYONE patch: shuffles cheese around. Seriously. A LOT of cheese.

Trade Routes - Regional Economy micropatch: fixes merchants inventory conflicts. The mods are largely incompatible (details), but with this this patch you can run them together anyway.

Sweets and Such - Baking Expanded SE patch: rebalances the new sweets, adds them to various season and region specific LL. This patch also has a Base Object Swapper ini to distribute the sweets, while keeping it on the DL (sweets will spawn very, very rarely).

Pheasant Encounters patch: ensures that Pheasants obey Seasonal Wildlife's and CACO's rules.

Additional Balancing Adjustments

This mod now has a child: Seasonal Foods - Tea Coffee Cocktails. It is a drinks expansion, adding 17 new drinks and dispersing them over different seasons and regions. 

To stop farmers from growing their crops in the winter, you should try Seasonal Alchemy Add-on - Critters and Fungi and Farms.

Skyrim Landscape and Water Fixes assigns ownership to crops to prevent easy stealing from poor farmers.

To stop barrels from providing you with food, you can use Garbage Loot - Barrels and Sacks. This mod is prefectly compatible, as it only edits container content of barrels, sacks, and Solstheim urns. With it you will no longer find easily available fresh food. You'll find spoiled food, common ingredients (dead bugs, moss, skeever tails, etc), and miscellaneous items.

To explore the world of Skyrim as a wandering drunk cuisine appreciator, try Alcohol Drunk Effect Redone.