There is perhaps no better answer to this question than the ongoing worldwide experiment sponsored by the Center for Innovation in Engineering and Science Education (CIESE). Open to students from ages kindergarten through Grade 12, the experiment asks participants to to boil a specific amount of distilled water on three different days, taking note of ambient temperature and other variable factors that may impact the boiling point, such as altitude. The International Boiling Point Experiment basically proves that there are many different boiling points for water.

Boiling Point in Controlled Temperatures 

However, in normal, controlled environments, the boiling point of water is 100 degrees Celsius or 212 degrees Fahrenheit, with the precise actual boiling point occurring just a shade below these round number temperatures.  The main game changer for a water boiling point is atmospheric or scientific experiment pressure. At lower pressures, the boiling point of water is lower; at higher pressures, the boiling point is higher. The reason for this is quite simple; additional pressure translates as increased resistance in the air to the release of liquid molecules turned into gas, thus requiring more energy to complete the reaction.

Planetary Example

The lowest air pressure so far known to man comes courtesy of NASA data gathered on the planet Mars.  As a result, the temperature range of liquid fresh water is reduced by a factor of ten. Rather than ranging from zero to 100 degrees Celsius, Mars water spans only zero to ten degrees Celsius. And at those ten degrees, much like on the highest of earth's mountain peaks, water on Mars comes to a boil. The low-temperature evaporation of Mars water presents a difficult challenge for NASA scientists trying to chart the possible past evolutions of life forms there. Presumably, on some planet yet to be discovered by man, the reverse is also true; a very high air pressure means a water boiling point of one thousand degrees.