Patrick, I usually use a combination. I find Clear Sky Clock gives a decent view, but is often not updated enough. I don't think they've updated their maps recently. Check it again later today. One sight that I and I know others use that really does tend to be more accurate is Skippy Sky Astronomy. http://www.skippysky.com.au/NorthAmerica/ Click on the NorthWest in the upper left and scrolls through the +6, +9, +12 to see the forecast (it defaults to total cloud cover; you can click on what you want to see i.e. seeing, transparency etc.). Remember the time is UTC so back off the 6 hours from the listed time. A little more complicated but much more accurate. Then with the NWS a lot of us use the Activity Planner: http://forecast.weather.gov/wxplanner.php?site=slc I usually set it for Temperature, Relative Humidity and Cloud Cover and set it from 0 to 100. Once the criteria is set with the location I hit submit under the town (or nearest town) and then you will get some colored line, in this case I got red for temperature, Green for Relative Humidity and Blue for Cloud Cover: http://forecast.weather.gov/MapClick.php?b0=t&b0mn=0&b0mx=80&b1=rh&b1mn=0&b1... After that I simply scroll the mouse along the one I want to view and the 3 will change by the hour. This is what I got from the tool for Stansbury Park: The temp goes from 70 degrees at 5pm to 60 degrees by 8pm to 54 degrees F by 11:00pm The Sky Cover goes from 42% at 5pm to 47% at 6pm and stays at 47% from 6pm til 11:00pm So based on what I see in Skippy and with the Activity Planner SPOC should have partly cloudy skies with about 40% to 50% coverage. For me this works with about a 90% accuracy but as with anything weather related, it can surely be wrong. Accu Weather matches the Activity Planner with a 45% cloud layer during the day and they rate viewing tonight as a 6/10 since there will be some clouds in the area. Hope it helps. http://www.accuweather.com/en/us/stansbury-park-ut/84074/hourly-weather-fore...