Game concept
Steppe Season
The game also links it as Steppe Seasons.
From the game's encyclopedia
A Steppe Season represents the current climate of The Great Steppe, and the effects that this has on County Fertility, as well as the actions that are available to involved Situation Rulers.
Steppe Seasons are independent to each region, and Nomadic Rulers may want to move to those with positive active Seasons.
On occasion, the same Season may occur in more than one Situation Region at a time.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Steppe Season is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "A Steppe Season represents the current climate of The Great Steppe, and the effects that this has on County Fertility, as well as the actions that are available to involved Situation Rulers." It is part of The Great Steppe. It covers Seasonal Prediction. The game also links it as Steppe Seasons. Patch 1.20.1.2, from game/common/game_concepts/mpo_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/mpo_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.