Although the early mornings are often cloudy in Nairobi the sun nearly always breaks through by mid-morning and throughout the year there is an average of nearly 7 hours of bright sunshine per day ; 30% more sunshine occurs in the afternoon than in the morning , so that westerly exposures receive more insolation than those facing east.

There is also considerably more sunshine during the 6 months that the sun is in the southern hemisphere, than when it is in north . Only occasionally during the rainy seasons , or in the months of June, July and August, do days occur with no sunshine at all. Even in the cloudiest month, August , there is an average of 4 hours sunshine per day.
 

Average numbers of hours per day of bright sunshine for each month of the year

January	February	March	April	May	June	July	August	September	October	November	December
8.9	9.5	8.7	7.0	5.7	5.8	4.4	4.2	5.9	7.0	7.0	7.9

Not only is the amount of sunshine considerable, but the quality of ultra-Violet radiation has been shown to be very high .