factor affact Critical micelle concentration

For anionic surfactant, the carbon chain within 8 to 16 carbons, increase 1 carbon, will decrease the CMC by half. I am talking about the same series of the surfactant. Same surfactant will have lower CMC when it has a branch.
The decrease of temperature means decrease internal energy of the system. Molecules arrange to form micelle do need energy. Particularly for anionic surfactants, increase temperature increase the solubility of the surfactants. However this is not true for non-ionic surfactant.
About increase salt, may decrease the solubility of the surfactant, this can lead to lower the CMC.
Talking about CMC you need to specify which type of surfactant.