2019 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 5 3 2 3 4 10 11 6 6 26 10 2 88 Monthly Average: 7.3 Partial 6 4 12 8 9 5 1 7 1 2 4 4 63 Monthly Average: 5.3 Spectroscopic 2 1 4 4 3 5 2 6 3 1 1 2 34 Monthly Average: 2.8 Cloudy 18 20 13 15 15 10 17 12 20 2 15 23 180 Monthly Average: 15.0 ------------------------------------------------------------------------------- Clear Hours 97 54 91 74 72 93 80 80 65 290 134 40 1170 Monthly Average: 97.5 Clear+Dark Hours 62 37 48 29 51 57 47 25 23 145 73 16 613 Monthly Average: 51.1 Mean Consec 1.7 1.0 1.0 1.0 2.0 2.0 2.8 2.0 2.0 6.5 2.0 1.0 Monthly Average: 2.3 Max Consec 3 1 1 1 2 3 5 2 4 15 3 1 Monthly Average: 3.4 ------------------------------------------------------------------------------- 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.