Lag Beomer always falls out on the 33rd day of the Omer or the Hebrew date of Yud Ches Iyar. This year it begins at sundown on May 25 and ends sundown on May 26. The day marks the passing anniversary of Rabbi Shimon Bar Yochai. He is the author of the well know mystic text that reveals the deepest secrets of Kabbalah- the Zohar.
There are lots of customs associated with the day. I will discuss a few. The most well know is lighting bonfires. Children collect wood weeks in advance for this ceremony. Crowds reach over 600,000 at the largest bonfire in Israel at Rabbi Shimon Bar Yochai's tomb in the northern village of Meron. Lighting bonfires commemorates the great light that Rabbi Shimon bar Yochai brought into the world via his mystical teachings. This was especially true on the day of his passing, Lag BaOmer, when he revealed to his disciples secrets of the Torah whose great depth of knowledge the world had yet to experience. The Zohar relates that the house was filled with fire and intense light, to the point that his students could not approach or even look at Rabbi Shimon.
Every Lag Beomer Eve, one family sponsors a bonfire in my community. It's a big merit to light the bonfire and that right is auctioned off. Children stay up past their bedtime, teens help mount the barricades and set up the 20 foot tall bonfire. Men and women also join the festivities. There is a live band, singing, dancing, and snacks.
It is a special day for blessings. There are numerous stories told of couples who could not have children, praying and giving charity at Rabbi Shimon's tomb and the next year having children. Chabad Chassidim who live in NY pray at the Ohel of the Lubavitcher Rebbe. On this auspicious day charity is given in multiples of 18. Lots of people donate food and liquid refreshments for the crowd at Rabbi Shimon's tomb. This too is a great merit and a receptacle for abundant blessings.
The well known custom in my community (Chabad) is the Lag Beomer parades. The Lubavitcher Rebbe initiated in the 1950s. He encouraged parades to be held all over the world to encourage Jewish unity and pride. When Lag Beomer falls out during the week, there is a rally for children either in front of Lubavitcher Headquarters on Eastern Parkway or like this year, in a park. When Lag Beomer occurs on a Sunday, a full on parade happens. The past few were called the Great parade, a theme song was created and t-shirts were for sale. Plans are made months before and logistics are discussed with police and city officials. Over 30,000 people attend the parade. People come from all over NY and from other states as well. The parade is taken very seriously. The parade starts off with superstars from the Jewish music world singing in concert. Then each school marches, some of them carrying self made banners. There are also yeshiva drum marching bands and rabbinic students dress up in clown and chicken costumes. Large flat TV screens are placed every few feet so everyone can see what's happening on stage. It's also streamed live online. Schools compete and try to outdo each other with floats. Each float has a different theme about Jewish or Chassidic concepts. I remember in high school we would stay up nights assembling the float and trailer. After the parade is over the floats are parked on different streets so the community can look at all the details. Rides and bounce-u are brought in to continue the fun after the parade. And of course barbecues finish off the fun filled day!