1231

By area

Asia

• April 9 - After a bizarre weather phenomena of yellowish clouds and dust chokes the air around Hangzhou, Song Dynasty, China, obscuring the sky and sun, a fire breaks out at night in the southeast of the city, which continues into the next day. Fighting the flames is difficult due to limited visibility. When the fires are extinguished, it is discovered that an entire district of some 10,000 houses in the southeast of the city were consumed by the flames.
• Mongol troops cross the Yalu River into Korea, then under the Goryeo Kingdom.

  Europe

• Italy: Emperor Frederick II promulgates the Constitutions of Melfi, a collection of laws for Sicily, as well as the edict of Salerno, regulating the exercise of medicine and separating the professions of physician and apothecary.
• Llywelyn the Great launches a campaign against the Norman lordships in Wales.
• Spain: The Castillans reconquer the city of Quesada.
• University of Cambridge granted a Royal Charter by King Henry III.

  By topic

Religion

• Ardengus becomes bishop of Florence.