2004 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 5 6 7 10 14 12 5 7 11 8 6 11 102 Monthly Average: 8.5 Partial 7 3 5 2 4 3 1 5 5 3 0 4 42 Monthly Average: 3.5 Spectroscopic 3 1 6 5 5 11 6 0 0 4 3 3 47 Monthly Average: 3.9 Cloudy 16 19 13 13 8 4 19 19 14 16 21 13 175 Monthly Average: 14.6 ------------------------------------------------------------------------------- Clear Hours 91 86 100 102 129 96 39 83 127 100 68 162 1183 Monthly Average: 98.6 Clear+Dark Hours 38 27 49 72 53 61 1 27 62 49 27 85 551 Monthly Average: 45.9 Mean Consec 1.0 1.5 2.3 2.5 2.3 2.4 1.7 1.8 2.8 1.6 2.3 2.2 Monthly Average: 2.0 Max Consec 1 3 3 5 5 4 2 4 4 3 3 3 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.