The Shulchan Aruch 551:11 mentions several customs regarding refraining from eating meat and drinking wine during the 3-week period.
The customs mentioned are:
- From the 17th of Tammuz
- From the 1st of Av
- The wek in which 9th of Av falls
While at first glance they seems based upon Chmura etc. there is really a good rationales for these customs.
The Mishnah in Ta'anit 4:x mentions that on the 17th of Tammuz the Korban Tamid ceased. Furthermore it mentions that at the advent of Av - reduce our Simcha Based upon the above 2 principles we can understand the foundation of 2 of the customs. In discussing this with my friend Mordechai Shaffier, he articulated the follow construct:
- Those who rerfain from meat/wine from the 17th of Tammuz do so out of "zecher lemikdash," i.e the custom commemorates the catastrophe of termination of the daily sacrifice- which is triggered on its very anniversary.
- Those who refrain from meat/wine from the 1st of Av do so because of the principle that since there is no Simcha WITHOUT meat/wine; therefore meat/wine produce Simcha. And since we are told to reduce simcha from the 1st of Av, therefore it flows from and follows that meat/wine must be abandoned on that date in order to reduce our Simcha.
The Fundamentalist Halachah is that wine and meat are prohibited ONLY on the eve of he 9th of Av. Yet these minhaggim have a solid root in the Mishnah itself, they flow from a very natural source - without being forced