During Advent many Catholics participate in what is commonly called the Rorate Mass, a votive Mass in honor of the Blessed Virgin Mary that is traditionally celebrated in a candlelit church.
The Mass receives its name from the first words of the opening chant in Latin, “Rorate caeli desuper, et nubes pluant iustum” (“Drop down dew, ye heavens, from above, and let the clouds rain the Just One,” Isaiah 45:8).
Historically this Mass was celebrated in the dark, only illuminated by candlelight and typically just before dawn. If timed correctly, by the end of Mass the entire church is filled with light by the sun. This speaks of the general theme of Advent, a time of expectation eagerly awaiting the arrival of the Son of God, the Light of the World.
Current regulations allow this special votive Mass to be celebrated on any weekday during Advent that does not have a special feast associated with it.
Many parishes celebrate this Mass on each Saturday of Advent, while others will reserve this Mass to the final week before Christmas.
The most common time for such a Mass is 6:30 a.m., though some parishes choose to celebrate it in the evening.
While the Rorate Mass is most popular in places such as Poland, it can also be found in many parishes in the United States.