There are a variety of vicious disasters that are part of the Anno 1404 game to add extra difficulty. Disasters can be turned on or off individually in Continuous Game. All disasters will receive a verbal warning and notification.
Fire: can break out randomly in the city. Can slowly spread. Even if fire is turned off, fires can still be started by mobs, arson spies, Thunderstorms, Volcanoes, Tornadoes and building damage. Peasants that are happy will work hard together to carry water-buckets to the fire and can usually put out a fire themselves. Fire station can be built to combat fires and roads can be upgraded to stone roads to allow quicker fire control. Fire damage can also be repaired by Carpenter's house, so there are many countermeasures to fire so it is the least threatening of the disasters.
Thunderstorm: thunderstorms loom over occidental islands (green islands) for several minutes. During a thunderstorm a few weaker buildings may be destroyed like growing fields if they get struck by lightning which can do approx 200 damage and set buildings on fire. The Thunderstorm is restricted to not often fall on main island and lightning usually does damage approx. 3 times. Also thunderstorms greatly reduce a player's visibility for the island. Thunderstorms are a large thick dark gray cloud, heavy rain and also have a water droplet camera lens effect, making visibility very low. The countermeasures are the same as fire, emergency service buildings Fire station and Carpenter's house.
Sandstorm: randomly covers most of an oriental island (desert islands) in a sandstorm for several minutes. Sandstorms can be really damaging to an oriental island economy because they "dry noria" the island and fields become 0% unproductive. The population can turn into a mob fast without both food and drink. Buildings can be slightly damaged in the darker parts of the sandstorm.
Plague: adds a green skull above a house and spreads randomly through houses slowly lowering population. If enough population is effected then foreigners will not trade with the island until the lengthy plague is cured. Can be countered with Surgery building. Beggars are said to bring Plague and therefore it is wisest to always reject them and as a nice added bonus your Patricians or Nobleman will reward you with a large sum of gold coins.
Tornado: the king of the disasters. The tornado should only be experienced by those who want to be punished brutally and don't mind rebuilding half their island. The only countermeasure are having emergency service buildings on hand to deal with the fire aftermath such as Fire station and Carpenter's house. However the Tornado mostly just sucks up entire houses but can also catch nearby buildings on fire. Visual reference.
Spy: added content with Venice expansion and acts as a disaster. A spy can be stopped by clicking on them in your main cities. Spy wear a medieval bird beak mask (called a Plague doctor costume in real history). A spy can cause various disaster effects and should be stopped by manually clicking on them or by building a Base of Operations. More info on Espionage.
Utilize emergency service buildings such as Fire station, Carpenter's house & Surgery. Always leave space near the center of your city for these buildings because they have a radius that they effect. If you want to save on the gold maintenance cost of the buildings, wait until the disaster occurs first, then build emergency service where it is needed.
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