Understanding land and sea breezes: how they can affect your sailing

What is a land breeze? 

A land breeze is a gusty wind that blows offshore (from the land to sea) in coastal areas mainly at night and early morning. During a clear night, the air cools over the land leading to an outflow of cooled air over the sea (cold air is heavier than warm air, so this outflow occurs downwards, into a valley). 

Why does it occur? 

The sea has a fairly stable temperature and, especially on a clear night, the land cools more than the sea. As the cool wind flows away from the land towards the warmer sea, the air gradually warms from the sea, dissipates and subsides. 

How powerful is a land breeze? 

The strength of a land breeze depends on the shape and steepness of the coastline. The wind is strongest in sloping valleys and narrow gorges, where wind speeds can be over 20 knots. 

Sailors, beware! 

In seas where high mountains stretch along the coast, the wind can be really strong and even dangerous. The Adriatic and the Velebit mountains are typical examples. Therefore, beware of anchoring in the southern bays in this area, where the wind from Velebit falls on steep and high slopes, and then accelerates in the valleys leading into these bays.  

Before anchoring, therefore, it’s always a good idea to check not only the shape and depth of the bay, but also the elevation and land relief above the bay — ⁠contour maps and the shape of the contours. 

What other terms are there for a land breeze? 

In some literature, land breezes are referred to as mountain breezes or katabatic winds. For our purposes, these terms can be considered synonymous.

What is a sea breeze? 

A sea breeze is an onshore wind (blowing from the sea to the coast) as a result of the sun warming the land. In a sea breeze, a closed system of air circulation is created — the breeze blowing from the water over the land is constantly supplied by the air flowing at higher layers offshore (from the land to the sea). This type of breeze is called a diurnal breeze. 

How does a sea breeze form? 

The air over the land heats up, expands and rises. This causes an excess of warm air at higher levels. If a gradient wind blows offshore from the coast, this gradient wind helps to move the excess warm air over the sea. At a certain distance from the coast, the excess warm air descends to sea level and replaces the air flowing landward. This leads to a continuous circulation and, depending on the rate the land heats up, the sea breeze intensifies. 

How powerful is a sea breeze? 

When a sea breeze occurs, its strength depends mainly on the direction of the gradient wind, the amount of sunshine and your distance from the coast - the closer you are to the coast, the stronger the sea breeze. The entire system of circulation can reach up to 50 kilometres from the coast. The strength of a sea breeze can range from a few knots at the edge of the system to around 20 knots near the coast. 

Windy.com states that 'such a breeze… can be very calm: 1–⁠5 meters per second.'

When to expect a sea breeze? 

Here's where you'll be disappointed — because it's not so much about the actual time as it is the amount of sunshine and the difference in temperature between land and sea. Therefore, the existence of a sea breeze, its strength and the time of its occurrence varies radically according to the seasons and the current weather. Often, a temperature difference of only a few degrees between land and sea is sufficient for a sea breeze to form. However, it can be generally said that sea breezes usually occur during the later morning/early afternoon under suitable conditions. It reaches its maximum around mid-afternoon (around 2–3 pm), then weakens and often only completely subsides at sunset. 

How to use sea breezes for sailing? 

Historically, fishermen have made great use of the breezes. They would set out to sea early in the morning with the wind at their backs and later in the day would return to the coast on a broad reach. Sailors can take inspiration from them too!

Sailing a sea breeze is fantastic! If a sea breeze develops, it produces wind towards the coast almost all day long. If you want to use the sea breeze effectively, sail closer to the coast. When a sea breeze forms, the wind blows perpendicular to the shore. With the gradual formation of an ever stronger circulation, the wind direction turns to the right along the coast until the breezes are almost parallel to the shore. 

Nothing is as simple as it may first appear and many other factors play a role in the formation and shaping of a sea breeze. If you would like to learn more about sea breezes, we recommend the books Weather at Sea by David Houghton and Wind Strategy (Sail to Win)  by David Houghton & Fiona Campbell, where you will find lots more practical advice and information related to sea breezes. 

We at yachting.com love the Windy app. Check out their textbook where you’ll find all the important weather formations clearly explained.  

City breeze 

Windy writes in its meteorological guide that a breeze is not just the domain of the sea. It occurs in cities too.  Buildings are heated by sunlight, creating a temperature difference between the city centre and the surrounding area. This difference can be as much as 8 degrees Celsius and causes the wind to move from suburban areas towards the city. However, this is all influenced by construction, street width, etc. 

Forest breeze 

A forest breeze is based on the principle that large, deep forests have a lower temperature during the day than the fields next to them. Most of the solar energy is therefore spent on evaporating moisture from the leaves rather than warming the forest. As a result, the wind moves from the field to the forest. 

Mountain breeze 

A mountain breeze blows towards the valley at night. It only occurs in calm weather without much cloud cover. It is generally weaker than a sea breeze.