Disasters occur randomly, they are marked by an Icon on the calendar to give you time to prepare. They are usually announced 3 months before they occur.
Neutral Events
Blood Moon
Map: Ragnarök only
During one month, 
attack of all units outside of their territory is increased by 50%. This event never occurs during winter.
Negative Events
Rat Infestation
Rats will devour a % of any 
Food not stored in Silos.
- Hard: 80% lost
- Medium 60% lost
- Easy: 20% lost
Rat infestation will also 
sicken a certain amount of clan members.
Earthquake
Damages up to 3 buildings. Buildings require 
Wood to Repair.
Blizzard
Occurs during winter. Reduces all production by 50%, and doubles firewood consumption. Stockpiling enough Food and Wood is the key to survive it.
Draugr Invasion
One 
Draugr will spawn out of each Draugr Portal on the map.
Fallen Sailors
Spectral Warriors will invade one of your shores and cause a reduction of 
-10 Happiness for as long as they are in your territory.
Attack of the Kraken
The Kraken roams around Northgard and punishes those who do not fear it, sinking boats and damaging ports. The Kraken attack lasts for 3 months. Kraken attacks can be avoided by stopping the raids before it starts or by building a Lighthouse.
Frozen sea
Map: Permafrost only
The sea freezes during winter, preventing all boat-related mechanics: 
Sailors, 
Mercenary raids, extra villagers from the Recruits fame bonus, and 
Thrall purchasing. Drakkars sailing at the beginning of the frozen sea will be immobilized until the end of the winter. This event can happen right after another event, therefore not being announced in the calendar.
Volcano Eruption
Map: Ragnarok only
The volcano will erupt and molten rock will fall on various tiles on the map. The number of molten rocks falling onto your territory will vary depending on the number of tiles you have colonized.
Each rock holds 
10 Stone. Unless the player manages to completely mine these rocks within 4 months, Rock Golems will spawn from them and attack any units in the tile. If a rock was only partially mined before the deadline, the Golem will spawn missing some HP.