Many years during the summer (especially July) there is a period of upwelling that lowers temperatures over the near shore waters. This is a result of the persistent south/southeast wind flow caused by the nearly stationary Bermuda high pressure ridge. Water transport in the upper oceanic layers is 90 degrees to the right of the wind flow (known as Ekman Transport) , which is directly away from the coast when the winds are predominantly south/southeast. Therefore colder water from below must upwell.

Periodic meandering of the Gulf Stream also occurs and induces upwelling. This may be due in part to the atmospheric forcing (high pressure ridge position/strength).

The upwelling usually subsides during August due to an overall diminishing of the winds (high pressure ridge sets up across the area).

There may be some correlation to the cooler near shore waters and increased intensity of afternoon thunderstorms. This would mainly be due to a slight increase in the strength of the winds behind the sea breeze boundary, which produces stronger convergence with the west coast sea breeze boundary.

The cooler waters would have no appreciable impact on a tropical cyclone. The reason for this is that a tropical cyclone covers hundreds of miles and the cooling near shore is on a much smaller scale.