I've always found car temperature readings to be not dissimilar to those of the nearest official sites - when I see pictures like this it does make me wonder how cold it really gets in sweet spots with no official station.
No thermometer here but it feels a little redundant just now to quote numbers - it's freezing! but lovely and sunny. I often find the main perk of cold spells during winter, and especially now given the strength of the sun, is that you can do a little bit of living room sunbathing