Hello From Airdrie, Alberta, Canada

Hi David, welcome to Radmon.
You've been online here for a week now, and your weekly graph shows an interesting daily rise near midnight UTC (is that 8:00 pm local?). Most of our detectors don't show such a large daily change (over 100%). Does your detector get heated somehow? It's also possible that these are actual events like Radon release. Is your detector indoors? Have there been unusual weather or pressure changes this week in Airdrie?

Yep I saw that as well and I have been trying to figure some reasonable explanation for it.
I am in Mountain Standard Time (-7 UTC) so that's about 5:00 pm my time.
It is indoors in a window but the sun is quite down by then (4:30 pm and it sets really fast this time of the year)
The window is facing west but no direct sunlight ever hits it as the sun is quite low on the horizon and there are a number of other houses blocking the west / south west view.
We have had lots of snow, ice fog, ice crystals but again nothing tonight and still the spike.
I am going to move it to an east window and see if that makes a difference.
If I see the spike again but in the morning then I won't panic too much and figure out where I can put it.
Cheers.