A friend from overseas asked me if I knew of the tradition of the Rorate Mass, in which a votive Mass to the Blessed Mother is celebrated just before dawn. The image left is from Assumption Grotto in Detroit. From a Polish-American cultural site:
The Rorate Mass takes its name from the first word of its introit (entrance song): “Rorate, caeli, desuper, et nubes pluant iustum,” or “Drop down dew, O heavens, from above, and let the clouds rain down righteousness.” It is a Mass in honor of Mary in which the interplay of light and darkness convey the meaning of Advent.Historically, it has been celebrated early on weekday mornings in darkness. As the Mass proceeds and sunrise approaches, the church becomes progressively brighter. Because it is a votive Mass to Mary, blue or white vestments are worn instead of the seasonal purple.
Sounds like a nice observance, but in all my years of liturgy, even in the Polish-rich land of Chicago, I’ve never encountered this before. Anyone else hear of it? Too bad it coincides with a very busy time for our students. This would be the kind of celebration that would have an appeal to many of them. My student liturgy team is winding down activity for the semester, as finals week is only 12 days away.
Catholic Sensibility 
My local parish has a Rorate Mass every year which is very well attended and followed by a community breakfast. A Rorate Mass in the EF was televised on EWTN a few years back. Here’s a link to the video if anyone’s interested.
I always associated Rorate Masses with German-speaking lands, though it does not surprise me that they also extend to areas settled by German speakers in what is now Poland and elsewhere, and then spread further from there.
As for vestment colors for these votive Masses of our Lady, I would think that would be white trimmed with blue, not blue (the limited old Spanish indult for the Immaculate Conception notwithstanding).
Rorate Mass is everywhere celebrated in Hungary, Transsylvania, in the whole former Austro-Hungarian empire. But in our days it’s mostly not longer a Maria-mass, it’s the normal daily Advent mass in purple, but it begins at 6 am or earlier. Usually people hold candles or other lights with them along the way to the churches. (sorry for my bad English).
It is a lovely Mass, and we have adapted it a little (evening, rather than early morning suits us better!). We are an Anglo Catholic church and have found the Rorate Mass enriches our keeping of Advent.
At St. Anne’s, t Catholic Church in San Diego, a Rorate Mass is celebrated at 5;30 am, during Advent, usually the closest saturday to Our Lady feast ( Immaculate Concepcion or Guadalupe) this year it will be on saturday december 8.A solemn Mass.
As a pastor,I introduced that mass in my Parish in Brussels; then in my two parishes in Vannes (France) great success among young and old; keeps us awake to welcome the on coming Christ!
St. Peter Church in Merchantville, NJ has a Rorate Mass at 6AM on a Saturday in advent – Solemn High Traditional Latin Mass. Indeed, it is very beautiful.
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We adapted ours for the evening. http://stchrysostoms.wordpress.com/2014/12/16/advent-rorate-mass/