A dramatic series of images showing just how quickly sea conditions can change has been published by coastguards as a warning ahead of this weekend.

The pictures were taken by Waves Surf School and posted on Facebook by Padstow Coastguard, before being shared by their colleagues in St Ives Coastguard Rescue Team.

Taken on the same day, over the course of just nine hours, they show a calm, flat sea at Harlyn Beach on the north coast at 9am, the swell starting to pick up by 12 noon and by 5.40pm the rough sea is filled with large waves and heavy spray flying up from the rocks as breakers crash into them.

Falmouth Packet:

The sea Harlyn Bay at 9am, 12 noon and 5.40pm on the same day  Picture: Waves Surf School/Padstow Coastguard

The warning comes ahead of rough sea conditions are forecast for this weekend. 

The shipping conditions in the Plymouth area of the shipping forecast, which covers the entire south coastline of Cornwall, shows southwesterly winds, veering westerly later, at 5 to 7 - just short of gale force 8, while the sea state will be rough, occasionally moderate.

In a post titled 'Take care on the coast this weekend!' Padstow Coastguard wrote: "There are rough sea conditions predicted this weekend, so please make sure you only visit beaches patrolled by our RNLI colleagues.

"A great example of how changeable conditions can be was captured in this image by Waves Surf School recently. Believe it or not, this was Harlyn Beach at 9am, 12 noon and 5.40pm on the same day!

"Please check the tide times, local conditions and listen to the lifeguards if you do head to the beach this weekend.

"Stay safe and if you see anyone in trouble on the coast then call 999 and ask for the coastguard."