Everyone knows that...

Human body temperature - Wikipedia
https://en.wikipedia.org/wiki/Human_body_temperature
In humans, the average internal temperature is 37.0 °C (98.6 °F), though it varies among individuals. However, no person always has exactly the same temperature at every moment of the day.

However, in recent Freakonomics podcast “Bad Medicine, Part 1: The Story of 98.6.”, a guest researcher cast doubt on that number (which from what I understand is from research 100+ years old).

In his study, Mackowiak found the actual “normal” temperature to be 98.2 degrees.

(i.e. 36.8 Celsius) What does actual scientific research say in 2016, as opposed to old medical textbooks?

The average rectal temperature is 36.85 °C

Relative to the average rectal temperature, other parts of the body are:

Mouth -0.45 to -0.30

Esophagus -0.30 to -0.20

Stomach -0.20 to -0.10

Vagina -0.05 to +0.05

Brain -0.25 to +0.05

For more information see Estimating changes in mean body temperature for humans during exercise using core and skin temperatures is inaccurate even with a correction factor which determines the mean esophagus, rectal and aural canal temperature as a function of minutes of exercise at two ambient temperatures (24 and 30 °C)

Mean rectal temperature at an ambient temperature of 24 °C at rest is:

36.82 °C with a standard deviation of 0.27 °C