Are they in full sun in the shade? What height are they at? What is the surface below them? All things which can affect the measurements.
There's three sensors spread out in various places in the garden I go for the average reading of all three one on the fence doesn't get the sun till after twelve noon at the earliest, the second one is on the facing fence behind my greenhouse in the shade soon after twelve noon and the third one is on the side of my workshop nearer to the house in the shade from about twelve onwards
The old mercury one is close by the second sensor in the shade both of them.
I've had this weather station with it's three sensors for some years now, it even shows the phases of the moon, barometer showing tendencies up or down, radio controlled clock, humidity, it's not a cheep and cheerful jobbie.
Everybody ignores me and walks off at home here if I try to relate any of the info it gives?
There's a lot of well sheltered reflected heat here it's always just that degree or so warmer any time of the year out at the back of the house and oh yes all sensors are residing atop grass and general garden greenery too.
I will be cross checking the accuracy of the sensors, just to keep myself happy, regardless of anyone else.
Regards ippy