Technically speaking there is no "in the sun" temperature because it would depend on how much thermal energy the thermometer material absorbs from light.
Exactly. Mass of air has temperature and an object like thermometer can come into equilibrium with air temperature.
On the other hand an object in sunlight will have temperature that has very complex relationship with a lot of parameters including shape of the object or windspeed.
Further, the object will not come into equilibrium and will show a gradient of temperature meaning the readout will depend on where you measure.
