The SA Weather Service (Saws) has warned of rough seas, along with strong to gale-force winds over the Cape areas.
The forecaster has issued an Orange Level 5 warning over parts of both the Eastern and Western Cape regions later on Monday.
"A tight pressure gradient between a cold front and a ridging high is resulting in strong winds that are enhancing the sea state," Saws said.
This means strong waves along the coast between Plettenberg Bay and Port Edward.
"Further, there is a full moon which could amplify the wave heights even further," Saws warned, adding that there could be abnormal or 'rogue' waves in the Agulhas current between Port Alfred and Port Edward.
Saws said this could impact on smaller vessels, with damage to beaches, dunes and estuaries.
Meanwhile, it's going to be a wet start to August for KwaZulu-Natal, Limpopo and Mpumalanga.
Saws said light rain can be expected along the eastern escarpment and along the KZN coastal areas, continuing along the southern and south-eastern coastlines.
According to Saws, on Wednesday and Thursday, there will be a light drizzle along the Limpopo and Mpumalanga escarpments.
The forecaster added that a high-pressure system will cause mostly dry to fine conditions in other parts of the country and along coastal areas.