I always suspect that they don't tell me the actual temperature. Maybe I am totally wrong but I suspect. I need to get my own physical thermometer not the digit

I always suspect that they don't tell me the actual temperature. Maybe I am totally wrong but I suspect. I need to get my own physical thermometer not the digital one in my room and outside my house and have a camera focussed on it. So that later I can speed up the video and see how much the weather varied the previous night.