The irritating thing about a sea breeze is that it usually occurs when there is very little wind elsewhere. One might reasonably hope the warm conditions which pertained in one's garden might be replicated near the coast a few miles away - but this is often not the case. Willows whiten, aspens quiver; Little breezes dusk and shiver, and the wind from the sea is not quite cold perhaps, but it is intrusive enough to make one wonder why one came.
The sea breeze occurs because of a developing contrast as a day progresses between the temperatures over land and sea. In the early morning there is little difference between the two; as the summer sun climbs higher in the sky, however, soil and rock quickly absorb its warmth, and heat the over-lying air - and it expands.
Remember the pressure at any point in the atmosphere can be thought of as the weight of the total amount of air directly above that point.
If you imagine a point some hundreds of feet above the ground, the expansion of the air in the lower layers due to solar heating will result in more air above that point than there was before. This means that at that level, pressure will be higher.
So what happens now? At that upper level, because of the high pressure, a drift of air develops out to sea.
This transfer of air in turn causes a drop in pressure at ground level over the land, and a corresponding rise in pressure at sea level some distance out to sea.
This pressure difference near the surface of the earth causes a wind to blow land-ward from the sea - the sea breeze. And the reason for its chilliness is obvious; air flowing towards you over a water surface, which at this time of the year may have a temperature in the region of 12 or 13 Celsius must inevitably feel cool in conditions when the air temperature might otherwise be in the region of 20 to 25 Celsius. Early in the day, the sea breeze blows directly from high pressure to low pressure at right angles to the coast, but as it becomes established, the rotational effect of the earth - the "Coriolis effect" - causes it to veer, as it does with all wind, so that it blows along the isobars, in this case, parallel to the coast.
This change can be noticed taking place gradually in the course of a warm sunny day, and as the temperature differences decrease towards evening, the sea breeze dies away altogether.