To replace a previous similar thermometer had passed away after years of loyal service, I bought it. What a disappointment! From the first rays of the sun falling on him the morning when it is still very cool to around 10 ° C (checked on another thermometer), it already displays 40 ° C !!!! I think there must be a design problem that makes a greenhouse the slightest presence of sunlight.
Conclusion: impossible to know what the temperature is.