2000 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 2 1 5 9 10 11 7 1 10 10 7 2 75 Monthly Average: 6.3 Partial 6 4 4 4 5 0 1 2 8 3 6 5 48 Monthly Average: 4.0 Spectroscopic 5 2 6 10 7 6 8 3 6 2 4 10 69 Monthly Average: 5.8 Cloudy 18 22 16 7 9 13 15 25 6 16 13 14 174 Monthly Average: 14.5 ------------------------------------------------------------------------------- Clear Hours 64 26 78 105 89 63 54 18 139 120 112 59 868 Monthly Average: 72.3 Clear+Dark Hours 62 15 40 73 59 34 21 2 68 49 41 41 505 Monthly Average: 42.1 Mean Consec 1.0 1.0 1.7 1.5 2.0 3.7 3.5 1.0 1.4 1.7 1.8 1.0 Monthly Average: 1.8 Max Consec 1 1 2 2 3 5 4 1 3 3 2 1 Monthly Average: 2.3 ------------------------------------------------------------------------------- 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.