Liquid nitrogen Dewar itself has no temperature, or room temperature, because it is filled with liquid nitrogen to have the temperature!
The temperature of liquid nitrogen is -196°C. The temperature among liquid nitrogen is all at -196°C, so it is often emphasized that the sample should be covered by liquid nitrogen.
However, liquid nitrogen Dewar has a natural volatilization rate, which may be 0.1 liters a day or 0.3 liters, both fast and slow depending on the caliber of the liquid nitrogen tank and the liquid nitrogen capacity.
As the liquid nitrogen evaporates, the sample will gradually reveal itself, and a small part of it is above the liquid nitrogen level.
Just like the dynamic evaporation loss of the liquid nitrogen tank, the temperature above the liquid nitrogen Dewar level is not well defined.
Because the temperature is influenced by the amount of liquid nitrogen remaining in the tank, the temperature of liquid nitrogen remaining more will be lower, the remaining less temperature will be higher, in short, above -196 ℃.
If you want to know the specific temperature you need to measure it yourself, you can also measure the overall temperature of the tank with the help of a liquid nitrogen temperature detector, and then make calculations to also get the temperature above the liquid level.
Also note that if the liquid nitrogen in the tank can no longer cover the sample, it needs to be filled with liquid nitrogen!
You can’t wait until the liquid nitrogen is almost finished evaporating; that kind of temperature fluctuation will probably affect the biological samples in the liquid nitrogen dewar.