Why snow does not falls in ooty even when it is at a much higher altitude than Nanital or any himalayan hill?

Answer 1

Surface temperatures and Atmosphere temperatures really matters............. Being Born and studied in OOTY I can just say this....................
Snow forms in the atmosphere, not at the surface. So snow can fall when surface temperatures are above freezing as long as atmospheric temperatures are below freezing and the air contains a minimum moisture level (the exact level varies according to temperature).

Answer 2

Cause of it's proximity to the equator, it falls in the region where sun is closer to earth than at Himalayan north. Now this is my hypothesis but wait for other answers before you reach conclusion.