During the night the Arno began to be in flood, although there had not been a drop of rain but the snow had melted suddenly, so that the river entered the town and flooded it as far as the Canto a Monteloro, and benches from the Church of Santa Croce floated across to that point.
And the water went into the Piazza del Grano, reaching more than half-way up the door of the apothecary's shop and past the Palagio del Podesta. The river overflowed its banks opposite Messer Bongianni's houses, and filled the Prato and the Via della Scala. Many mules and horses were drowned in their stables, and all the wine-casks went floating about, mostly towards the Arno. This flood had come suddenly.
The Pope sent us an Indulgence, to be obtained by attending six churches: Santa Maria del Fiore, the Nunziata dei Servi, Santa Croce, Santa Maria Novella, Santo Spirito, and Sa' Jacopo in Campo Corbolini.(1) And it began on this day and lasted till Easter. Everyone who wished to obtain it had to visit these six churches on three mornings, confessing and doing penance; and had to lend aid, at the said churches, to the forces sent against the Turks.
(1) This church, which was founded in the year 1000, is preceded by a little peristyle closed by wooden gates, as the church is no longer in use. On the capitals of the columns are the arms of the Alberti. In 1206 it passed into the possession of the Knights of Jerusalem, and a good many of their tombs are in the interior. It stands in the Via Faenza, and must not be confounded with either of the two other churches of the same name: San Jacopo tra Fosse, and San Jacopo in Borgo San Jacopo. (Trans.)
There was a furious storm, the air seeming for some time to be full of bursting fireworks, so incessant was the thunder and lightning. When the storm was over, about eight different places were counted which bore visible traces of having been struck. One was the Campanile of Santa Croce; another the Porta a Pinti, etc. But it did not cause much damage, and no one was killed.
Entry from "A Florentine Diary" by Luca Landucci:
Fra Girolamo preached, and ordered that alms should be given for the Poveri Vergognosi(1) in four churches: Santa Maria del Fiore, Santa Maria Novella, Santa Croce, and Santo Spirito; which were collected on the following day, Sunday. And so much was given that it was impossible to estimate it: gold and silver, woollen and linen materials, silks and pearls and other things; everyone contributed so largely out of love and charity.
(1) The Company of Buonuomini, who care for the Poveri Vergognosi, was formed before 1521, and used to care for the wants of the prisoners in the Stinche and the Bargello. They met in the old church of San Martino, to which offerings were brought, and they later extended their administrations to other honourable poor in the city. In the church of San Martino the twelve Buonuomini are painted in twelve frescoed lunettes. (Trans.)
Landucci, Luca, trans. Alice de Rosen Jervis, J.M. Dent & Sons, 1927. "A Florentine Diary", p. 74