1988 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 1 12 10 3 15 1 2 5 13 9 8 9 88 Monthly Average: 7.3 Partial 5 3 4 2 2 0 3 4 1 3 3 7 37 Monthly Average: 3.1 Spectroscopic 6 3 8 7 5 13 2 2 10 7 6 1 70 Monthly Average: 5.8 Cloudy 19 11 9 18 9 16 24 20 6 12 13 14 171 Monthly Average: 14.3 -------------------------------------------------------------------------------- Clear Hours 43 153 129 36 127 7 29 59 108 109 111 151 1062 Monthly Average: 88.5 Clear+Dark Hours 29 86 71 6 77 4 23 55 68 47 53 76 595 Monthly Average: 49.6 Mean Consec 1.0 2.4 2.0 1.0 3.8 1.0 1.0 1.7 2.6 1.5 1.6 1.8 - Monthly Average: 1.8 Max Consec 1 4 3 1 9 1 1 2 8 2 2 3 9 Monthly Average: 3.1 -------------------------------------------------------------------------------- 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.