It’s been over a week now since the new weather station (Acurite Pro model 06004) went operational in the back gardens. There have been signal dropouts and there has been cold temperatures (-20C), so we assumed it was the cold weather affecting the 4AA alkaline batteries powering the transmitter.
They were replaced 3 days ago with 4AA lithium batteries, rated for -40C.
And we still had signal dropouts!
So last night the receiver/display was moved from the front of the house to the rear of the house, closer to the transmitter, with fewer walls to penetrate, and with fewer sources of RFI between the transmitter and receiver.
The signal immediately jumped to 100% and has been solid for 12 hours now.

The issue is, we had 100% signal a *lot* when the station first went in.. and it got progressively worse and more intermittent over time.
Hopefully not a weather station failure in progress..
Only time will tell.

Updated 2019Dec13 – two days later the signal strength has remained strong and mostly consistent… just a few blips here and there of signal drop.