2008 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 4 4 13 13 9 14 2 4 9 12 9 2 91 Monthly Average: 7.6 Partial 4 7 7 5 5 2 1 1 5 5 2 8 52 Monthly Average: 4.3 Spectroscopic 3 5 5 9 8 8 6 0 7 8 1 5 65 Monthly Average: 5.4 Cloudy 20 13 6 3 9 6 22 26 9 6 18 16 154 Monthly Average: 12.8 ------------------------------------------------------------------------------- Clear Hours 78 86 163 149 92 105 20 36 115 164 120 72 1200 Monthly Average:100.0 Clear+Dark Hours 15 61 91 40 50 39 18 7 48 76 53 60 558 Monthly Average: 46.5 Mean Consec 2.0 1.3 1.9 2.6 1.5 2.0 2.0 4.0 2.3 3.0 2.3 1.0 Monthly Average: 2.2 Max Consec 3 2 5 5 3 4 2 4 4 4 4 1 Monthly Average: 3.4 ------------------------------------------------------------------------------- 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.