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• The standard temperature of photographic solutions (i.e., developer, stop bath, fixer, and rinse water) when processing film is 20 degrees Celsius/68 degrees Fahrenheit. Film and photochemical manufacturers normally provide an information sheet listing alternative time and temperature combinations for various developers and other photochemicals. Care must be taken not to use too high a processing temperature, as it may cause permanent damage to the negative ("reticulation").
• The temperature noted above applies to b&w film. The C41 process for color is 100F, which is more difficult to maintain throughout the process.

  In addition, reticulation is caused by extreme changes in temperature, not merely processing too warm. It is difficult to cause reticulation in modern film. One last nit-pick: you don't develop negatives, you print them. You develop film.