Cloud cover [%]: 90 80 70 60 50 40 30 20 10 0 Transparency: Poor Below Average Average Above average Transparent Seeing: Bad Poor Average Good Excellent Darkness: -4 -3 -2 -1 0 1.0 2.0 3.0 3.5 4.0 4.5 5.0 5.2 5.4 5.6 5.8 6.0 Wind [km/h]: >72 46..72 28..45 19..27 9..18 0..8 Humidity [%]: <29 30..35 35..40 40..45 45..50 50..55 55..60 60..70 65..70 70..75 75..80 80..85 85..90 90..95 95..100 Temperature: <-35 -35.-30 -30.-25 -25.-20 -20.-15 -15.-10 -10.-5 -5.0 0.5 5.10 10.15 15.20 20.25 25.30 30.35 35.40 >40

It's the astronomer's forecast. At a glance, it shows when it will be cloudy or clear for up to the next two days. It's a prediction of when Toronto, ON, will have good weather for astronomical observing. The forecast data comes from those very cool guys at the Canadian Meteorological Center.CMC's numerical weather forecasts are unique because they are specifically designed for astronomers. But they have 763 forecast maps. It can be a chore to find the one you want.

So, I (Attilla Danko) wrote a script to generate the images like the one above which summarizes CMC's forecast images just for Toronto and the surroundings out to about 15 Kms.

There are charts for 4021 locations.

(C) 2010 Attilla Danko.