2018 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 3 5 2 5 14 20 3 5 13 1 9 2 82 Monthly Average: 6.8 Partial 5 6 3 5 6 1 0 5 5 8 4 10 48 Monthly Average: 4.0 Spectroscopic 5 2 5 6 3 2 2 1 3 2 4 0 35 Monthly Average: 2.9 Cloudy 18 15 21 14 8 7 26 20 9 20 13 19 190 Monthly Average: 15.8 ------------------------------------------------------------------------------- Clear Hours 71 92 27 76 130 144 21 65 147 61 134 83 1051 Monthly Average: 87.6 Clear+Dark Hours 30 48 2 60 62 59 7 27 88 18 93 47 541 Monthly Average: 45.1 Mean Consec 1.5 1.7 2.0 1.3 2.3 4.0 3.0 2.5 2.2 1.0 2.3 1.0 Monthly Average: 2.1 Max Consec 2 3 3 2 3 5 3 4 7 1 5 1 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.