2017 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 4 5 1 5 9 13 3 4 5 22 0 7 78 Monthly Average: 6.5 Partial 4 3 9 11 6 6 1 7 10 4 9 7 77 Monthly Average: 6.4 Spectroscopic 1 0 10 5 6 1 1 3 3 2 3 4 39 Monthly Average: 3.3 Cloudy 22 20 11 9 10 10 26 17 12 3 18 13 171 Monthly Average: 14.3 ------------------------------------------------------------------------------- Clear Hours 65 75 64 110 91 112 25 64 112 253 47 138 1162 Monthly Average: 96.8 Clear+Dark Hours 59 38 44 60 56 57 13 46 98 117 27 72 693 Monthly Average: 57.8 Mean Consec 2.0 1.7 1.0 1.7 1.5 2.6 3.0 2.0 1.3 5.5 0 1.8 Monthly Average: 2.0 Max Consec 3 2 1 2 3 7 3 3 2 9 0 4 Monthly Average: 3.3 ------------------------------------------------------------------------------- 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.