Just a note. The temperature issue is more critical for C-41 COLOR film, than for C-41 chromogenic b/w film. You can be "off" a bit more with the b/w and still get good negatives. The reason for this is that the b/w only has one dye that has to form, while the color film has three color dye forming layers and they all have to form at once within a set amount of time and be more or less "equal" in their development,..so the film will balance within normal color-balance parameters.