The Celsius scale was developed in the early 18th Century by Swedish astronomer Anders Celsius (who else would he name it after?). His initial scale was different than the one used today, in that 0C was the boiling point of water and 100C was the freezing point. It wasn't until after his death in 1744 that the scale was reversed to its modern setup. A 100 degree system makes sense to a lot of people, in that it falls in line with the base-10 setup of the metric system (10mm=1cm, 100cm=1m, 1,000mL=1L).
If you head overseas in the future and find yourself watching a local forecast where temperatures are in Celsius, there is a formula to convert Celsius to Fahrenheit and back.
(F) = (C) x 9/5 + 32
(C) = (F - 32) x 5/9
|Freezing Point of Water (Rounded)||0||32|
|Boiling Point of Water||100||212|