I changed the battery in the weather station, because in cold weather it was reporting low and we really don’t want to lose any data.
Unfortunately, it picks a random station ID on restart! My display software selects one station ID to display (in case there are other weather stations nearby – the base station does the same thing). That turns out to be a bad idea if you want to see the historical data! I’ll need to enhance my code to display data from two station IDs, and do something clever with the rainfall (which has reset to zero).
Edit: Whew, fixed it. Bit of a horrid hack – I’ve hardcoded the old station ID and pre-battery-change rainfall, and arranged that it “corrects” the recent data. All-time rainfall is still wrong, but I’ll sort that another day – it’s bedtime!
For future reference, I’ve attached the weather station manual (thanks Maplin!).