Seasons

Seasons.rms
Based on the 4 seasons in a year, with a 25% chance of loading up a Winter map, Spring map, Summer map, or Autumn map.
Official in-game description
measured on replays site statistics calculated from game values

Variants measured on the ranked games analysed by AoE Buddy. Biomes (terrain, winter or desert scenery) will be detailed once they are read from the replays.