2007 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 9 4 7 7 6 11 0 6 9 11 5 5 80 Monthly Average: 6.7 Partial 6 8 1 2 2 4 1 4 4 7 7 3 49 Monthly Average: 4.1 Spectroscopic 3 4 9 3 6 6 1 7 3 8 7 9 66 Monthly Average: 5.5 Cloudy 13 12 14 18 17 9 29 14 14 5 11 14 170 Monthly Average: 14.1 ------------------------------------------------------------------------------- Clear Hours 152 100 78 75 53 96 4 65 112 116 97 82 1030 Monthly Average: 85.8 Clear+Dark Hours 89 30 40 54 12 48 1 37 47 102 45 46 551 Monthly Average: 45.9 Mean Consec 3.0 1.0 1.4 1.4 2.0 2.8 0 2.0 2.3 1.6 1.2 1.7 Monthly Average: 1.7 Max Consec 4 1 3 3 3 5 0 3 3 3 2 2 Monthly Average: 2.7 ------------------------------------------------------------------------------- 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.