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30-Year Average Annual Data

Station: Missoula,MT

Latitude (N): 46.92 Longitude (W): 114.08

Elevation (ft): 3189

Incident Solar Radiation, Global (Btu/sq.ft./day):

Horizontal: 1190 Vertical North: 360 Vertical East: 750 Vertical South: 940 Vertical West: 740

Heating Degree Days (HDD), base 65 degrees F: 7792

Cooling Degree Days (CDD), base 65 degrees F: 280

Temperature (degrees Fahrenheit):

Average: 44.3 Daily Minimum: 32.3 Daily Maximum: 56.3

Humidity Ratio (lb. water per lb. dry air): 0.0047

Wind Speed (mph): 6.4 Clearness Index (Kt): 0.52 * Precipitation (inches): 13.4

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Sources of information

Solar, temperature, degree day, humidity and wind was obtained from The Solar Radiation Data Manual for Buildings, produced by the National Renewable Energy Laboratory's (NREL's) Analytic Studies Division under the Resource Assessment Program, which is funded and monitored by the U.S. Department of Energy's Office of Solar Energy Conversion. For more detailed information please visit : , Interpreting the Data Tables.

Precipitation data was obtained from the National Climatic Data Center, a program of the National Atmospheric and Oceanic Administration. Select historical data by location from:

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Definition of Terms

Incident Solar Radiation - Global Radiation (Btu/sq.ft./day)
"Global radiation is the total radiation received by the window and is the sum of the direct beam radiation component, sky radiation, and radiation reflected from ground in front of the surface." Data is provided for five windows, horizontal and north, south, east and west facing vertical windows. The annual average is comprised of 30 years (1961 - 1990) of average annual data.

Degree Days -
"Degree days indicate heating and cooling requirements of buildings. They are defined as the difference between the average temperature for the day and a base temperature [in this case 65 degrees Fahrenheit]. If the average for the day (calculated by averaging the maximum and minimum temperature for the day) is less than the base value, then the difference is designated as heating degree days. If the average is greater than the base value, the difference is designated as cooling degree days."

Clearness Index (Kt) -
"The clearness index (Kt) is the station's global horizontal solar radiation divided by its extraterrestrial horizontal radiation. Because clouds decrease the amount of solar radiation reaching the earth, stations in cloudy regions will have lower values for Kt than stations in regions will fewer clouds."

Precipitation -
Based on 30-year (1971 - 2000) Normal.
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