2020 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 3 9 1 12 12 14 7 7 13 18 11 9 116 Monthly Average: 9.7 Partial 4 5 5 7 6 4 6 4 6 4 4 10 65 Monthly Average: 5.4 Spectroscopic 13 6 1 1 4 2 3 3 0 4 1 1 39 Monthly Average: 3.3 Cloudy 11 9 24 10 9 10 15 17 11 5 14 11 146 Monthly Average: 12.2 ------------------------------------------------------------------------------- Clear Hours 69 135 42 145 128 117 77 75 147 220 141 191 1487 Monthly Average: 124 Clear+Dark Hours 26 63 22 73 82 61 18 20 48 122 68 77 680 Monthly Average: 57 Mean Consec 1.0 1.8 1.0 2.0 1.7 2.8 1.4 3.5 2.2 2.6 1.8 1.8 Monthly Average: 2.0 Max Consec 1 4 1 4 3 9 2 6 5 9 4 3 Monthly Average: 4.3 ------------------------------------------------------------------------------- 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.