A chronicle of 1851 tells the discovery of the Marian image that was the origin of the construction of the church: a fire of a house along the walls had caused the fall of timber and debris, which were not removed until 1367, when in the area the excavation was carried out to create the new Reno Canal, now buried, and to bring water to the mills. During the works, a painting of Madonna with Child emerged from the rubble.
The image was placed in the Oratory of San Bartolomeo di Reno, built in 1204 and owned by the Compagnia dei Mercanti. Attached to this church there were rooms, initially used as a shelter for pilgrims to Rome, then in 1330 were used as a hospital for the poor and in 1527 for the reception of orphans. The image also took the name of Madonna dei Putti di San Bartolomeo, and became the object of great veneration following the episode of the miraculous recovery of a blind man.
In 1561, the year of ongoing drought with the threat of a terrible famine, the painting was repeatedly conducted in procession to the four ancient city crosses. The processions took place at the beginning of August, and at the end of the month the long-awaited rain came. From this event the Marian image takes her new name as the Our Lady of the Rain. Since then, every year, the faithful brings the image in procession to one of the four crosses of the city, making it stand for eight days, at the end of which it was taken to the churchyard of San Petronio for the blessing of the city.
In 1604 it was moved from the oratory to the church below, where on the 21st of March of the same year it was crowned with a silver crown weighing over half a kilo, adorned with precious stones. In 1621 the confreres of San Bartolomeo asked and obtained the image with the name of Madonna della Pioggia, which still today distinguishes it. As proof of its main prerogative, the dates on which the rain was obtained through its intercession have been handed down on time.
In 1732 it was placed in the niche above the high altar, instead of a terracotta statue of San Bartolomeo. From that moment the church assumed the double dedication, in San Bartolomeo and the Madonna della Pioggia (Our Lady of the Rain), and the traditional procession (which continued until the removal of the crosses during the French domination) was moved to the third Sunday of Lent.
Today, the Sanctuary of the Madonna della Pioggia becomes a center of “rain of mercy” where The Chaplet of the Divine Mercy is prayed every day thanks to the zeal of the Polish nuns of the sanctuary. (video below in italian explaining the great “rain of mercy” in this Sanctuary where the Divine Mercy Chaplet is said everyday)