The BBC and National Public Radio have reported that a team from the University of Tel Aviv is using the signals from "mobile phone masts" (cellular phone base stations) to measure rainfall. The researchers say their technique is more accurate than other methods. As you may have guessed, the system works by measuring the strength of the signals from the satellite. Rain increases attenuation and signal levels drop. The researchers said the technique should also work for measuring snowfall, hail or fog. The BBC quoted Professor Hagit Messer-Yaron explaining this by noting that in the days before cable television, "Whenever there was a storm outside, you had a bad picture on your TV. This is well known."
The scientists said that when estimates from the cell site monitoring were compared with radar and rain gauge readings, they closely matched. However, there are more cell sites than rain gauges and radar often has gaps in coverage.
It seems to me that receivers monitoring broadcast signals could be used to gather similar data, over a wider range of frequencies -- from 55 to 700 MHz, although the lower TV band frequencies are somewhat less subject to rain attenuation than higher frequency cell phone signals. Noting the multipath on DTV signals, which appears noise like over approximately 6 MHz, might yield additional information on rainfall and storms.