Why do icicles usually form more on the south sides of buildings?
Because the sun shines more directly onto the slope and walls on the southern side than the northern warming the roof above the freezing point even if the air (and surfaces not directly in the sun) are below freezing. The ice or snow melts and trickles down the roof until a drop is hanging in the sub-freezing air where it freezes again. Even if it’s still in the sun, there is no heat absorbing or reflecting surface behind it. More water trickles over that frozen surface, some of it never freezes and drips off, some is so warm it melts some of the ice already formed, but enough freezes to form the icicle. The larger an icicle gets the more heat it can absorb without melting so the larger it gets the faster it grows. Since the afternoon temps are generally warmer than the morning, icicles also are more likely to form on the western sides than the eastern.If the air under a roof is warm, cause you don’t have enough insulation in your attic, icicles can form all around. Of course in the so
