Aloha,
I've hacked together a station to report to wunderground with a 5 in 1, a Raspberry Pi, rtl_433, and some Python code. One thing I found is the sensor continues to report the rain totals for days and sometimes weeks after the rain event. I thought this was a daily total and should reset every 24 hours at midnight, but after yesterday's rain it is still reporting the same total accumulation:
{"time" : "2020-02-11 08:32:34", "model" : "Acurite 5n1 sensor", "message_type" : 49, "sensor_id" : 711, "channel" : "A", "sequence_num" : 0, "battery" : "OK", "wind_speed_kph" : 5.139, "wind_dir_deg" : 337.500, "rain_inch" : 0.520}
{"time" : "2020-02-11 08:32:34", "model" : "Acurite 5n1 sensor", "message_type" : 49, "sensor_id" : 711, "channel" : "A", "sequence_num" : 1, "battery" : "OK", "wind_speed_kph" : 5.139, "wind_dir_deg" : 337.500, "rain_inch" : 0.520}
{"time" : "2020-02-11 08:32:34", "model" : "Acurite 5n1 sensor", "message_type" : 49, "sensor_id" : 711, "channel" : "A", "sequence_num" : 2, "battery" : "OK", "wind_speed_kph" : 5.139, "wind_dir_deg" : 337.500, "rain_inch" : 0.520}
The only other thing I could think is maybe it's 24 hours from the last detected rain? That was about 15 hours ago.