2020 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 3 9 Monthly Average: Partial 4 5 Monthly Average: Spectroscopic 13 6 Monthly Average: Cloudy 11 9 Monthly Average: ------------------------------------------------------------------------------- Clear Hours 69 135 Monthly Average: Clear+Dark Hours 26 63 Monthly Average: Mean Consec 1.0 1.8 Monthly Average: Max Consec 1 4 Monthly Average: ------------------------------------------------------------------------------- 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.