2013 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 11 10 6 12 9 15 1 2 13 15 6 13 112 Monthly Average: 9.3 Partial 6 6 4 6 9 6 2 3 3 10 6 7 68 Monthly Average: 5.7 Spectroscopic 3 3 5 5 8 3 1 2 2 1 3 0 36 Monthly Average: 3.0 Cloudy 11 9 16 7 5 6 27 24 12 5 15 11 148 Monthly Average: 12.3 ------------------------------------------------------------------------------- Clear Hours 180 154 85 134 109 126 15 31 143 228 109 199 1513 Monthly Average:126.1 Clear+Dark Hours 85 74 35 42 46 65 6 23 50 114 65 93 698 Monthly Average: 58.2 Mean Consec 2.8 2.5 1.2 2.4 1.8 3.0 1.0 1.0 2.6 2.1 1.0 2.6 Monthly Average: 2.0 Max Consec 6 4 2 7 2 5 1 1 4 4 1 6 Monthly Average: 3.6 ------------------------------------------------------------------------------- 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.