# Does solar radiation stimulate formation of clouds?

Observing the sky for multiple months during winter and spring I noticed that on cloudy days sunset correlates with clearer sky than at daytime. And backwards, several tens of minutes after sunrise clouds appear seemingly out of nowhere. This made me wonder: does solar radiation somehow stimulate formation of clouds — and is this really a known effect, or just my somehow biased impression?

I live at $60^\circ\mathrm N\,30^\circ\mathrm E$ if this matters.

• Weather can be highly regional and depend on a variety of local factors. Can you give us more information about the location? – macco May 29 '17 at 11:54
• @macco $60^\circ \mathrm N\,30^\circ \mathrm E$. – Ruslan May 29 '17 at 12:15

You seem to be right at the coast of the Baltic Sea. During the day the land gets warmer than the Sea due to the different heat capacities of water and land. Thus when the land cools down at sunset this will create a breeze that moves from the land towards the ocean. At sunrise the opposite is true. The cold land will heat up faster than the Sea which creates a Sea breeze from the Sea towards the land. When the cold air from the Sea meets the warmer air from the land the rising warm air will condense and form clouds as seen in the image below.

During a sunny day, evaporation of water is more likely, and so is the formation of clouds. Note that besides solar radiation there's another factor here: humidity. A dry environment would not produce clouds