As compared to gloomy days, do “sunny days” put you in a good mood? If you’re like many people , the answer is “yes”.

In a study of more than 1,200 people, researchers found that daily weather factors such as temperature, precipitation and length of day can alter a person’s emotional state. Of all the weather factors, however, “sunshine” can have the most profound effect.

The most likely reason is because sunshine affects people in a physiological manner.

When the human brain detects sunlight, our bodies produce serotonin, a chemical which promotes happiness and well-being. By contrast, when the brain detect darkness, our bodies produce melatonin, a chemical which promotes sleep cycles.

Sunlight — quite literally — leads to happiness.

Understanding the effect of sunlight on human mood, therefore, we must consider the nation’s “sunniest cities” as more than just a novelty list. It may be a link to personal well-being, too.

From the National Climactic Data Center, these are the Top 10 Sunniest Cities in the United States :

1. Yuma, AZ : Sunny on 90% of all days
2. Redding, CA : Sunny on 88% of all days
3. Las Vegas, NV : Sunny on 85% of all days
4. Phoenix, AZ : Sunny on 85% of all days
5. Tucson, AZ : Sunny on 85% of all days
6. El Paso, TX : Sunny on 84% of all days
7. Fresno, CA : Sunny on 79% of all days
8. Reno, NV : Sunny on 79% of all days
9. Flagstaff, AZ : Sunny on 78% of all days
10. Sacramento, CA : Sunny on 78% of all days

The sunshine rankings of other noteworthy cities include Key West, FL (#12 with 76% sunshine); Denver, CO (#30 with 68% sunshine); and Seattle, WA (#165 with 43% sunshine).

At the bottom of the list is Juneau. Just 30 percent of the Alaskan capital city’s days are sunny.

The complete Sunshine Rankings as listed by Metropolitan Area is available on the NCDC website.