1984 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 9 13 9 9 11 13 1 0 11 10 8 1 95 Monthly Average: 7.9 Partial 1 0 2 2 1 2 0 2 2 3 4 4 23 Monthly Average: 1.9 Spectroscopic 3 3 2 4 8 2 0 1 4 3 0 0 30 Monthly Average: 2.5 Cloudy 18 13 18 15 11 13 30 28 13 15 18 26 218 Monthly Average: 18.2 -------------------------------------------------------------------------------- Clear Hours 109 142 109 99 86 100 7 8 101 114 113 37 1025 Monthly Average: 85.4 Clear+Dark Hours 77 76 68 49 54 44 4 8 48 51 56 13 548 Monthly Average: 45.7 Mean Consec 1.5 2.2 1.3 1.8 1.8 4.3 1.0 0.0 2.8 1.4 1.6 1.0 Monthly Average: 1.7 Max Consec 3 5 2 3 3 7 1 0 6 4 3 1 Monthly Average: 3.2 -------------------------------------------------------------------------------- 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.