In general, if there are light gradient winds on the coast (the wind being due to a high- or low-pressure system) in any direction and there is a difference in temperature between sea and land, there is likely to be a sea breeze.
On a sunny day in particular the land heats up quickly, causing the air to rise. Replacement air is drawn in over the coastline – a sea breeze (fig. 1).
With a sea breeze in the same direction as the gradient wind, you may experience strong winds. Equally, if they are opposed and the gradient wind is strong, there may be a flat calm in the afternoon.