|For the enemy, see Weather (virus).|
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the lowest level of the atmosphere. Weather refers to day-to-day temperature and precipitation activity, whereas climate is the term for the averaging of atmospheric conditions over longer periods of time. When used without qualification, "weather" is generally understood to mean the weather of Earth.
In the Mega Man franchise, due to advanced technology, weather can change on both natural and unnatural ways. Depending on the weather, the terrain can be affected in a number of ways such as removing, obscuring, or adding obstacles.
|Default weather with no additional effects.|
|Warm weather overheats Croak Hoppers in the Mega Man X series. In Mega Man Zero 4, the heat in Sol Titanion's stage is too intense even for Zero, requiring him to hide in shadows to avoid overheating. Sunny weather also affects the power of the Gun del Sol EX in the Mega Man Battle Network series.|
|Introduced in Mega Man 4, the wind from rainy weather affects the player's mobility, adding or reducing speed to jumps depending of its direction. Acid rains like Rain Flush and Nightmare Rain cause damage. In the Mega Man X series, Sole Solars are innactive on rain, while Croak Hoppers become more active.|
|Strong winds can push or pull the player, depending of its direction, making it easier or harder to jump over obstacles.|
|Reduces mobility or visibility, depending of its intensity. In Mega Man 7 it is actually benefical as the snow will cover the transparent platforms in Cloud Man's stage.|
|Foggy / Misty / Cloudy|
|Reduces visibility, which can be dangerous for players unfamiliar with the terrain, like making it hard to see pits in Pegasolta Eclair's stage. In the Mega Man X series, it is beneficial as Sole Solars, Croak Hoppers, and Sky Farmers are innactive during this weather.|
- In Mega Man X2 and Mega Man Xtreme 2, the Weather Crystal can change the weather in the Weather Control Center, Wire Sponge's stage.
- In Mega Man X6, the Weather Analyze causes acid rain in Rainy Turtloid's stage. Acid rain can also appear in other stages due to the Nightmare Phenomenon.
- In the first Mega Man Zero game, Contrainer can create strong winds, the rain in the area showing the wind's direction. TechTwister can generate a twister around itself.
- In Mega Man Zero 4, the Weather Changing System (ウェザー・チェンジング・システム) allows players to decide the weather from the stages of the Einherjar Eight Warriors, which affects the terrain that Zero travels through. Stages which have a flashing border indicate a harder weather setting, whilst non-flashing ones will be easier. This can be changed right before the mission briefing. Playing on a harder stage may amplify the boss's strength as well as grant them the use of their EX Skill. Instead of finishing at S or A rank like previous games, completion of a stage in its harder form will grant Zero an EX Skill, while easier ones will not, and also result in a penalty at the Result screen.