it has more meanings than one.
First,it’s the body temperature in the morning with a slight fever,which can become a real fever later in the day.
It’s a sign of a disease or the first hint of passion
.Also,in feminin cycle,it’s the temperature of ovulation.
This explaination it’s from Beineix in an interview.
“37.5 [degrees] le Matin.” Translated this means 37.5 degrees celcius in the morning