@badnetmask I don't have an outdoor Hue sensor, but I have an indoor one and I had the same question: why was the temperature and illuminance data from it so old, especially when the motion sensor worked great?
I believe it's because it only sends an updated measurement if the values change significantly, so as to save battery. Other sensors I've gotten since then give me control of those thresholds, but this Hue sensor does not. (In its defense, it was very first one I bought and has been going strong for years now.)