1986 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 8 3 6 4 6 11 8 1 6 8 9 2 72 Monthly Average: 6.0 Partial 5 3 4 5 6 2 5 1 4 6 3 8 52 Monthly Average: 4.3 Spectroscopic 6 4 3 8 4 3 1 4 1 2 7 3 46 Monthly Average: 3.8 Cloudy 12 18 18 13 15 14 17 25 19 15 11 18 195 Monthly Average: 16.3 -------------------------------------------------------------------------------- Clear Hours 125 48 88 66 79 85 84 12 86 123 120 81 997 Monthly Average: 83.1 Clear+Dark Hours 94 5 38 41 47 51 53 5 62 50 76 50 572 Monthly Average: 47.7 Mean Consec 4.0 1.5 2.0 1.0 2.0 2.8 1.6 1.0 1.0 1.3 1.3 1.0 Monthly Average: 1.7 Max Consec 7 2 3 1 3 5 3 1 1 2 3 1 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.