2011 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 5 7 3 8 8 22 6 3 6 15 5 8 96 Monthly Average: 8.0 Partial 8 4 6 4 8 3 1 4 1 4 2 4 49 Monthly Average: 4.1 Spectroscopic 4 6 2 2 4 2 4 2 3 2 4 4 39 Monthly Average: 3.3 Cloudy 14 11 20 16 11 3 20 22 20 10 19 15 181 Monthly Average: 15.1 ------------------------------------------------------------------------------- Clear Hours 119 100 60 88 101 169 47 46 67 188 67 126 1178 Monthly Average: 98.2 Clear+Dark Hours 62 50 44 66 75 77 12 26 42 87 34 67 642 Monthly Average: 53.5 Mean Consec 2.5 2.3 1.5 1.6 2.0 5.5 2.0 3.0 1.5 3.0 1.3 2.7 Monthly Average: 2.8 Max Consec 4 5 2 4 5 8 3 3 2 5 2 5 Monthly Average: 4.0 ------------------------------------------------------------------------------- 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.