I do not consider myself to be a weather expert but, as a Yachtmaster Examiner and Instructor, I am expected to have a basic knowledge. With that understanding of the fundamentals of weather plus fourteen years experience of sailing and motor cruising along the Algarve coast, here is my view on the mechanics of the Algarve summer weather.

I think of the Algarve summer as beginning in June and ending in September. For most of that period there is high pressure centred on the Azores which extends right across the Iberian peninsular. High pressure areas do not have frontal systems and so as long as our barometers are showing high pressure the weather is always good. As the wind revolves around a high pressure area in a clockwise direction our wind comes from the north for most of this period. This is known as the gradient wind. The strength of this wind is no more than force 2 or 3, however during the afternoon and early evening on the west coast this will back into the north west and increase to force 6 or 7 as a result of the on-shore breeze effect. This will make passages northwards from Cape St Vincent hard work in the afternoon and early evening. A better time to sail or motor northwards is between 9 pm and about 11 am the next day.

The onshore breeze effect, mentioned above, is a result of the heat of the sun warming up the air above the land. This hot air rises and sucks cooler air in from above the sea. Early and late in the summer this often creates a string of clouds along the coast caused by the moisture content in the warm rising air meeting colder air at a higher level and condensing to form cloud, which is usually ‘burnt off’ by the sun as the day progresses.

On the south facing Algarve coast there will be a force 2 to 3 gradient wind from the north to north west during the night and until about 10 am when the wind will drop to nothing. Then an hour later at about 11 am the wind will pick up again from somewhere between west and south. This is the combination of the onshore breeze effect from the south and the gradient wind from the north.

By mid afternoon this onshore breeze will quickly veer back into the north west and often increase to force 7 or more. This wind appears to be at it’s strongest between Portimao and Lagos, where at times there can be violent gusts of up to 40 knots. The reason that the wind veers and increases in the mid afternoon is that Andalucia and Morocco have heated up enormously during the course of the day and have a massive onshore breeze effect pulling the colder air from over the sea to their north west which, combined with Portugal’s northerly gradient wind and the onshore breeze effect on the west coast, totally cancels out our local Algarve onshore breeze giving us a very strong north westerly wind for the rest of the afternoon and evening.

I was asked recently why do we sometimes get a very strong northerly wind in the Algarve in the middle of the night. The explanation for this is exactly the opposite to the reason for the on-shore breeze effect during the day. The land cools off quite quickly during the night and with no cloud cover so does the air, however the sea remains much the same temperature at night and warms up the air over the sea which rises and sucks the cooler air over the land south to replace the air that has risen, this off-shore breeze will be noticeable for up to about seven miles inland and when combined with the force 2 to 3 gradient wind may reach force 5 or more with occasional violent gusts.

We do occasionally get a Levanter (east wind). This will be caused by a high pressure area centred in France, Germany or the north of Spain. This wind brings warmer water from the Andalucian coast to our beaches in the Algarve and usually in the summer good weather.

In my next ‘On board’ page I will be writing about our currents and tides which I hope you will find useful and interesting. Meanwhile I hope that you have been enjoying the wonderful weather that we have been having as much as I have.