Every summer about this time, gray tree frogs converge on Iowa ponds for mating and egg-laying, and with hundreds of frogs involved, the calling becomes a roar. They are commonly heard in forests from late spring to mid-summer, especially on quiet rainy days, but more frequently at night. Around these small breeding ponds, however, is probably the only time you'll hear them in super-concentrated numbers. The video doesn't do the overall noise level justice, because it is truly deafening. | Iowa