The sixth month of the
Aztec Xiuhpohualli (calendar) was
Etzalqualiztli. It marked the end of the dry season and the beginning of the rainy season. In comparison to the western calendar, the month covered the dates we know as May 24 through June 12.
The month was for the eating of maize-bean stew. Reeds were brought from the lakes to make new mats and adornments for the temples. Tlaloques were honored and great festivals to the rain makers were held. Priests fasted for four days and let their own blood. After the fast the priests would take a ritual bath and then throw themselves into the water of Lake Tlaloc and splash around pretending to be ducks. The priests would also carry jars full of human hearts to the mountains to honor Tlaloc. They would throw the hearts into the water and it was believed that the water would foam and shake in response to the hearts being received. The priests would also put jade into the water for Tlaloc as well as tie jade to poles which were hung just above the water line in the hopes that Tlaloc would fill the lake to touch the jade.
Sources:
http://www.ancientmexico.com/articles/aztec_religion.htm
http://www.crystalinks.com/aztecalendar.html
http://www.azteccalendar.com/introduction.html