HoMM 5 >Magic >Weather

There are various kinds of weather. Cloudy weather is neutral and all other forms of weather have a bonus for one allignment and a penalty for another (might has no bonus or penalty). What weather it is, will depend on a chance and on terrain. For example, on snow terrain, the weather will often be snowy and never cindering, but it can be cloudy, misty or sunny.
If it is a certain type of weather, there is a 10% chance that a storm of the associated weather will occur. Storms have all kinds of effects, but one kind of weather will lead to one kind of storm. For example, if you start a fight in snowy weather, there is a 10% chance that a blizzard will occur. Every schools of magic, except for Life, has a L4 spell that summons a storm, which belongs to their beneficial weather. Since there is no storm associated with sunny weather, Life has the "Fairweather" spell, which sets the weather to cloudy or sunny (depending on level of caster) and nullifies all further storm, weather or weather spell effects.

Notice that when I write "benefit", it can also mean that everyone except for that alignment suffers a penalty, in which cases the penalized alignment suffers extra penalty. For example, everyone but order moves slower in snow, and Archeon also get reductions in attack and morale.

*Note: Except for "Firestorm" and "Fairweather", there are no storm spells in the spell descriptions. Perhaps, I'll edit them in later, but it is not high on my list of priorities, right now.