1997 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 1 4 10 1 2 13 10 1 7 16 6 5 76 Monthly Average: 6.3 Partial 4 5 3 5 0 6 4 5 6 3 2 5 48 Monthly Average: 4.0 Spectroscopic 8 4 8 9 12 5 3 2 3 7 5 4 70 Monthly Average: 5.8 Cloudy 18 15 10 15 17 6 14 23 14 5 17 17 171 Monthly Average: 14.3 -------------------------------------------------------------------------------- Clear Hours 39 81 102 37 15 118 84 32 97 190 78 95 968 Monthly Average: 80.7 Clear+Dark Hours 17 25 48 16 13 46 63 13 54 120 63 35 513 Monthly Average: 42.8 Mean Consec 1.0 1.0 1.7 1.0 1.0 2.6 3.3 1.0 3.5 2.7 1.5 1.7 Monthly Average: 1.8 Max Consec 1 1 4 1 1 6 8 1 4 5 2 2 Monthly Average: 3.0 -------------------------------------------------------------------------------- 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.