Hey there mate ;)
While measuring the surrounding air, it is approximately 35.2°C. Now after breathing in and exhaling out, we find that the air exhaled out is 44.2°C.
This is because, when breathing in, only oxygen and some moisture content is present, but in exhaled air, it contains heavy CO2 (carbon dioxide), other gaseous wastes and huge amount of water vapour.
As our body organs function tirelessly, more heat is produced, therefore, the temperature shown by thermometer is greater in exhaled breath instead of surrounding air.