1993 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 2 1 4 4 14 19 12 5 21 7 11 9 109 Monthly Average: 9.1 Partial 2 2 7 4 1 0 4 1 4 2 5 3 35 Monthly Average: 2.9 Spectroscopic 1 0 5 15 8 4 5 3 4 7 2 7 61 Monthly Average: 5.1 Cloudy 26 25 15 7 8 7 10 22 1 15 12 12 160 Monthly Average: 13.3 -------------------------------------------------------------------------------- Clear Hours 34 24 80 53 108 133 102 44 216 74 158 130 1156 Monthly Average: 96.3 Clear+Dark Hours 18 3 29 22 43 76 35 35 85 16 48 34 444 Monthly Average: 37.0 Mean Consec 1.0 1.0 2.0 1.0 3.5 3.8 2.0 2.5 5.3 1.4 3.7 1.3 Monthly Average: 2.4 Max Consec 1 1 2 1 6 9 4 3 11 3 6 2 Monthly Average: 4.1 -------------------------------------------------------------------------------- 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.