I'm having the same / a simular issue of temperature related readings, but at a different temperature level (for me it must be > 14 degree). I massure the dew point as well (temperature = orange, dew point = yellow). It looks to be more related to water in the air than only to temperature.
@zboblamont have you been finally been able to find a solution?
I want to thank @FcNanoLed. I had long thought about a serial gateway. This would be a way to add I/O to a linux computer. In the process of trying to help, I built up a linux machine running virtual box. In the virtual machine I ran Home Assistant The not well documented part of that was to connect the USB port of the computer to the virtual machine (settings-->USB-->USB Device Filters) (note that one can buy a refurbished PC for about the same price as an equivalently configured RPi)
So thanks for the inspiration!
@mvader Turn the time delay adjustment preset on your PIR module to the minimum.. Now try it.. You will not get a continuous output..Also, prepare the circuit using a long wire from the back to the sensor of your module.