Sea water temperature: your complete guide

Ever find yourself caught out by chilly sea temperatures when on holiday? Well no more - welcome to your complete guide to finding idyllic warm water, perfect for any holiday. Read on to see how the world's oceans warm and move, and where to go on holiday with truly delightful conditions for swimming, snorkelling and more.

Sea Water Temperatures

Understanding sea temperatures: the basics

Factoring in the sea temperature is often overlooked by those planning a holiday, and it's easy to see why: if you're heading to a warm and sunny coast, it's fair to assume that the sea will also be warm enough to swim in. However, what goes on under the waves greatly affects the temperature of the sea - of course, the weather above water plays a part but everything from the currents, wind and location, to the time of year and your choice of ocean contribute to the temperature of any given sea.

Swimming in Lanzarote in November © Antony Hollingworth - Flickr Creative Commons
Swimming in Lanzarote in November © Antony Hollingworth - Flickr Creative Commons

The average sea temperatures given in our climate guides, which come from satellites that continuously monitor the world's oceans, refer to the sea surface temperature, which includes the top few metres where you're likely to swim and snorkel. Naturally, sea temperatures vary around the world, with highs of around 34°C in the Persian Gulf and lows in the region of -2°C (the temperature at which water freezes) near the poles.

If you're planning a holiday and trying to work out what the ideal sea temperature is for you, typically anything between 18°C and 26°C is considered to be comfortable for swimming, although this is somewhat down to preference. It's also worth remembering that while it may be warm at the surface, the deeper you go, the colder it gets. Read on to find out more about how sea temperatures are governed, and where in the world you can find the warmest seas for your next holiday.

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Understanding sea temperatures: map, facts & figures

Unsurprisingly, the majority of the sun's energy is focused on those parts of the earth that most directly face the sun - the equatorial regions - and it is here that the warmest air and sea temperatures are found. If there was no atmosphere this is the way things would stay but with air able to flow so freely a natural pattern of rising and falling streams of air is established from equator to poles that gradually redistributes thermal energy from the tropics to higher latitudes, and vice versa.

Sea temperature map showing sea surface temperature in August © www.weather2travel.com
Sea temperature map showing sea surface temperature in August © www.weather2travel.com

It is the prevailing 'trade winds' near the equator and the 'mid-latitude westerly winds' that do most of the work, and they in turn drag surface seawater with them in the same direction as they blow.

In the North Atlantic, northeast trade winds blow off the coast of West Africa, dragging the warm sea surface waters of the tropics westwards until they start to flow up the east coast of the United States. Here, they eventually meet the prevailing westerlies at around 45° north that push the waters eastwards, and finally southwards back towards Africa.

How trade winds and westerlies affect ocean currents © Brooks/Cole - Thomson
How trade winds and westerlies affect ocean currents © Brooks/Cole - Thomson

Importantly by this stage, much of the energy of the warm water has been absorbed by the cooler waters and atmosphere of the North Atlantic, so the returning waters are much cooler than they were. This circular pattern occurs in most oceans of the world with the direction of flow mirrored in the southern hemisphere. What is most noticeable is that the western boundaries of the world's oceans tend to be warmer than the eastern.

These currents are well established and operate much like clockwork. There are however, times when the natural flow is interrupted, such as during El Nino years, when sea temperatures in the tropical Eastern Pacific are as much as 3°C warmer for a season or two, and those in the Western Pacific a touch cooler. If you are travelling to the Pacific coast of Costa Rica or Mexico during an El Nino event you will notice it, as the ocean is unusually warm.

Guide to the world's ocean currents - courtesy of Dr. Michael Pidwirny
Guide to the world's ocean currents - courtesy of Dr. Michael Pidwirny

When it comes understanding sea temperatures for your holiday, it's best to check which of the world's currents you'll be faced with, especially if you're hoping to go swimming in the sea. There are a few good examples of popular holiday destinations where the current is cooler than many expect:

  • Algarve & Canary Islands - both sit in the cold Canary Current, which flows south from the North Atlantic
  • California - it doesn't put surfers off, but the eastern Pacific is surprisingly chilly thanks to the cold California Current, especially in the north
  • Cape Town - you may see plenty of African Penguins but you're unlikely to take a dip as the cold Benguela Current flows round this point of South Africa

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Finding the perfect sea temperature

What really matters when it comes to planning your holiday is where in the world you will find truly warm sea temperatures, ideal for swimming, snorkelling and making the most of your precious time off.

As we mentioned, it is generally accepted that the most comfortable temperature for swimming is somewhere between 18°C and 26°C. A look at the annual averages for a few of the most popular European holiday destinations at the height of summer quickly shows you where you will find the warmest sea temperatures in this region:

  • Algarve, Portugal - peaks at around 21°C in August and September
  • Tenerife, Canary Islands - peaks at around 23°C from August to October
  • Majorca, Balearic Islands - peaks at around 25°C in August
  • Cyprus - peaks at around 27°C in August
  • Alanya, Turkey - peaks at around 28°C in August
Coron Island, Philippines © GreenArcher04 - Flickr Creative Commons
Coron Island, Philippines © GreenArcher04 - Flickr Creative Commons

If you're hoping for even warmer sea temperatures, you will have to consider travelling further, typically to destinations in the tropics. Popular places to go with truly inviting sea temperatures that surpass 28°C, and that can be booked at an affordable price, include:

  • Bali, Indonesia - peaks at around 29°C from November to May
  • Cancun, Mexico - peaks at around 29°C July to October
  • Cuba - peaks at around 30°C in August
  • Sri Lanka - peaks at around 30°C in April
  • Dubai, UAE - peaks at around 33°C in August

Of course, these destinations aren't specific to summer holidays (in fact, we wouldn't recommend Dubai at the height of summer as it's simply far too hot), however this clearly shows the jump in sea temperature that you can expect to find at different times of year when you travel to the tropics.

Snorkelling

Warm waters and ideal snorkelling conditions don't always go hand-in-hand. While shallow water reefs flourish in warm sea temperatures, corals also require the very clearest seas to thrive; they won't grow if there is sediment in the water, or if conditions are too acidic. So if you're hoping to combine warm seas with some tip top coral and marine life on your holiday, look no further than these destinations which offer some of the finest conditions for catching a glimpse of colourful life in the ocean:

Young boy snorkelling in a warm clear tropical sea © BlueOrangeStudio - Fotolia.com
Young boy snorkelling in a warm clear tropical sea © BlueOrangeStudio - Fotolia.com

There's no way round it: understanding sea water temperatures is a complex issue, and we've barely scratched the surface of what influences the movement and temperature of water around the globe. However, hopefully you're now armed with a enough information to ensure that when it comes to planning your next holiday, you aren't caught out by cold sea temperatures that keep you from enjoying the beach.

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More holiday weather parameters:

Sea water temperatures by month

Below is the Sea water temperatures levels for popular holiday destinations around the world by month. Select a destination to see more holiday weather parameters.

Sea water temperatures in January

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Sea water temperatures in February

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Sea water temperatures in March

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Sea water temperatures in April

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Sea water temperatures in May

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Sea water temperatures in June

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Sea water temperatures in July

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Sea water temperatures in August

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Sea water temperatures in September

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Sea water temperatures in October

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Sea water temperatures in November

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Sea water temperatures in December

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