Here I add some results:
Only USB - Vcc = 5V
Celsius: 41.79
Kelvin: 314.94
Celsius: 41.79
Kelvin: 314.94
Celsius: 41.79
Kelvin: 314.94
Only USB - Vcc = 3.3V
Celsius: 23.24
Kelvin: 296.39
Celsius: 23.24
Kelvin: 296.39
Celsius: 23.24
Kelvin: 296.39
With adopter - Vcc = 5V
Celsius: 23.24
Kelvin: 296.39
Celsius: 23.24
Kelvin: 296.39
Celsius: 23.24
Kelvin: 296.39
With Adopter - Vcc = 3.3V
Celsius: 3.22
Kelvin: 276.37
Celsius: 3.22
Kelvin: 276.37
Celsius: 3.22
Kelvin: 276.37
Temp reading in case when Arduino was connected through USB only and Vcc = 3.3V is exactly equal to Arduino plugged in with adopter and Vcc = 5 V.
Strange, isn't it?