I have just finished upgrading a weather station I am building, and have found that all of the sensors that send pulses to convey their data, which is read by interrupts in the python software (the rainfall and wind speed sensors) encounter sporadic bursts of very large amounts of false pulses at the same time. This has resulted in rainfall in excess of 60mm, and wind gusts in excess of 90mph over the past few days when it has been completely sunny and still.
I was already using a low pass filter, and the bouncetime parameter in python, and never had anything anywhere near this extreme before. In fact, I was hoping that my replacement of the thinner cable on the rainfall sensor with thicker, better cable would have reduced this already small problem to zero, so was very surprised to find this problem much worse. It affects all sensors using pulse output, and it hits them both at the same time.
If it is of any use, this upgrade installed a 12V power supply to power a new sensor (in addition to the existing 5V RPi supply). Could that be generating noise? But then it only happens sporadically, not constantly. See the links below for the past 3 days of rainfall, which shows the problem. It has not even been cloudy for these days, and the false pulses seem to last for a period after the initial surge. Any help with stopping this problem is greatly appreciated.