The warming trend of the summer, which most people enjoy, is the root cause of the storms that will frustrate those who wish to spend their time outdoors and under the sun. The temperature difference between land and ocean is what causes sea breeze storms to pop. The key points to understand before getting in to the science behind the sea breeze circulation are as follows;
1) Land heats and cools faster than the ocean
2) Warm air rises
3) Cool air falls
4) Rapidly rising air causes storms
As the sun comes up in the morning, it starts heating both the land and the ocean. The land will heat faster (see point 1) than the ocean, allowing the air over the land to heat faster than the ocean air. The hot air over land then rises (point 2). As it rises, it creates a pressure difference over the land and ocean. This pressure difference pushes the hot air that has risen out over the ocean, where it then cools and falls (point 3). The pressure difference then sucks the cool ocean air in over land to take the place of the air that has risen, creating a circulation of air over land and sea. As this circulation intensifies, the air rises faster over land, and this rapidly rising air causes thunderstorms to form (point 4) and thus complicating plans for outdoor activities.
Timing the occurrence of sea breeze storms is always difficult, as moderate to heavy cloud conditions can delay daytime heating and therefore slow the development of the circulation. So while forecasters know there will be storms, pinpointing the exact location and time is extremely difficult. But if you just have to have a time table of when the rain will hit, a general rule of thumb is storms will form on the shore in the morning while inland storms will form in the afternoon.