Sunshine hours in Boulder: 3,105 hours a year, month by month

Boulder gets 3,105 hours of sunshine a year on average (8.5 a day). Sunniest month: July with 325 hours. Every month, measured 1961–1990.

• Boulder gets 3,105 hours of sunshine a year on average, 8.5 a day – 70% of the astronomically possible. The sunniest month is July with 325 hours (10.5 a day), the dullest November with 194 (6.5 a day).
• Number 95 of 311 large cities in the United States.
• Nearest weather station: Denver/Stapleton Int'l AP CO, 44 km away – 1961–1990 average, NOAA.

Sunshine hours month by month

• January: 215 h · 6.9 h a day · 72 %
• February: 211 h · 7.5 h a day · 71 %
• March: 256 h · 8.3 h a day · 69 %
• April: 276 h · 9.2 h a day · 69 %
• May: 290 h · 9.4 h a day · 65 %
• June: 315 h · 10.5 h a day · 70 %
• July: 325 h · 10.5 h a day · 71 %
• August: 306 h · 9.9 h a day · 72 %
• September: 272 h · 9.1 h a day · 73 %
• October: 249 h · 8.0 h a day · 72 %
• November: 194 h · 6.5 h a day · 65 %
• December: 196 h · 6.3 h a day · 67 %

Questions about sunshine hours

• How many hours of sunshine does Boulder get a year? On average over 1961–1990 the sun shines in Boulder for 3,105 hours a year – 8.5 hours a day and 70% of the time the sun is above the horizon.
• What is the sunniest month in Boulder? July, with 325 hours of sunshine, 10.5 a day on average. The least sun comes in November: 194 hours, 6.5 a day.
• Is Boulder a sunny city? Among the 311 large cities in the United States with measurements, Boulder ranks number 95.
• Where do the figures come from? From the WMO climate normals 1961–1990 as archived by NOAA. There are no newer figures: the US stopped measuring sunshine duration in the 1990s. Boulder uses the station Denver/Stapleton Int'l AP CO, measured 1961–1990.
• What counts as an hour of sunshine? By the World Meteorological Organization's definition the sun is shining once its direct radiation exceeds 120 watts per square metre. Just after sunrise and before sunset it is often too weak – which is why even deserts never reach 100%.

The sunniest large cities: United States

• 1. Phoenix: 3,873 h a year
• 2. Las Vegas: 3,826 h a year
• 3. Tucson: 3,806 h a year
• 4. Reno: 3,647 h a year
• 5. Sacramento: 3,609 h a year
• 6. Fresno: 3,565 h a year
• 7. Chico: 3,542 h a year
• 8. Colorado Springs: 3,463 h a year
• 9. Albuquerque: 3,414 h a year
• 10. Amarillo: 3,298 h a year

The cloudiest large cities: United States

• 1. Pittsburgh: 1,972 h a year
• 2. Anchorage: 2,063 h a year
• 3. Syracuse: 2,120 h a year
• 4. Seattle: 2,170 h a year
• 5. Columbus: 2,182 h a year
• 6. Grand Rapids: 2,188 h a year
• 7. Buffalo: 2,206 h a year
• 8. Meads: 2,259 h a year
• 9. Cleveland: 2,281 h a year
• 10. Rochester: 2,299 h a year

The sunniest large cities in the world

• 1. Mexicali: 4,017 h a year
• 2. Phoenix: 3,873 h a year
• 3. Las Vegas: 3,826 h a year
• 4. Tucson: 3,806 h a year
• 5. Ciudad Juárez: 3,763 h a year
• 6. Reno: 3,647 h a year
• 7. Dubai: 3,610 h a year
• 8. Sacramento: 3,609 h a year
• 9. Victoria de Durango: 3,573 h a year
• 10. Fresno: 3,565 h a year

The cloudiest large cities in the world

• 1. Chengdu: 962 h a year
• 2. Chongqing: 985 h a year
• 3. Sukabumi: 1,082 h a year
• 4. Glasgow: 1,153 h a year
• 5. Tanjung Pinang: 1,172 h a year
• 6. Medan: 1,201 h a year
• 7. Samarinda: 1,275 h a year
• 8. Sungai Penuh: 1,311 h a year
• 9. Limerick: 1,339 h a year
• 10. Huaihua: 1,352 h a year

• Data: NOAA, WMO climate normals of sunshine duration, 1961–1990 average, public domain. Possible hours: time between sunrise and sunset.