2012 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 3 2 6 1 19 22 0 0 8 12 14 4 91 Monthly Average: 7.6 Partial 4 7 8 11 7 3 1 4 5 6 4 3 63 Monthly Average: 5.3 Spectroscopic 8 7 6 4 1 5 1 1 5 11 5 3 57 Monthly Average: 4.8 Cloudy 16 13 11 14 4 0 29 26 12 2 7 21 155 Monthly Average: 12.9 ------------------------------------------------------------------------------- Clear Hours 62 67 112 80 173 167 7 19 113 161 187 73 1221 Monthly Average:101.7 Clear+Dark Hours 25 44 56 48 150 91 5 5 73 84 96 51 728 Monthly Average: 60.7 Mean Consec 1.0 1.0 1.5 1.0 3.2 4.4 0 0 2.0 1.7 2.8 1.0 Monthly Average: 1.6 Max Consec 1 1 2 1 10 9 0 0 3 4 4 1 Monthly Average: 3.0 ------------------------------------------------------------------------------- Definitions: Photometric - cloudfree dusk-to-dawn. Partial - at least 3 consecutive cloudfree hours during the night. Spectroscopic - less than about 1 mag. extinction throughout the night. Cloudy - cloudy. Clear+Dark Hours = photometric hours with moon absent. Mean Consec = mean number of consecutive photometric nights during the month. Max Consec = maximum number of consecutive photometric nights during the month.