Sea temperature and swimming season in Shenzhen
The sea off Shenzhen is comfortable for swimming from March to December. It peaks at 29.5°C in July and drops to 17.7°C in January.
Month by month
Sea temperature, the air you climb out into, and the wind that decides how that feels.
| Month | Sea | Air | Wind | Feels | What to wear |
|---|---|---|---|---|---|
| January | 17.7°C | 18.2°C | 3.2 m/s | Bracing | 3/2 mm full suit |
| February | 18.5°C | 23.1°C | 3.0 m/s | Bracing | shorty, or nothing if you are acclimatised |
| March | 20.9°C | 23.4°C | 3.2 m/s | Comfortable | shorty, or nothing if you are acclimatised |
| April | 23.6°C | 25.7°C | 2.8 m/s | Very comfortable | none, or a rash vest |
| May | 26.8°C | 27.6°C | 2.9 m/s | Bath-like | none needed |
| June | 28.5°C | 29.9°C | 2.6 m/s | Bath-like | none needed |
| July | 29.5°C | 30.2°C | 2.6 m/s | Bath-like | none needed |
| August | 29.2°C | 30.6°C | 1.9 m/s | Bath-like | none needed |
| September | 29.2°C | 29.6°C | 2.8 m/s | Bath-like | none needed |
| October | 27.8°C | 26.2°C ↓ | 3.5 m/s | Bath-like | none needed |
| November | 24.0°C | 25.6°C | 2.9 m/s | Very comfortable | none, or a rash vest |
| December | 20.3°C | 20.6°C | 3.5 m/s | Comfortable | shorty, or nothing if you are acclimatised |
Air is the average daily maximum — roughly what you would meet swimming in the middle of the day. An arrow marks months where the air is colder than the sea.
When in the day can you swim?
Daylight and burn risk by month, in Asia/Shanghai local time.
| Month | Sunrise | Sunset | Daylight | Peak UV |
|---|---|---|---|---|
| January | 07:06 | 18:00 | 10h 54m | 6.5 |
| February | 06:55 | 18:20 | 11h 25m | 8.5 |
| March | 06:32 | 18:32 | 12h 00m | 10.8 |
| April | 06:03 | 18:43 | 12h 40m | 12.7 |
| May | 05:43 | 18:56 | 13h 13m | 13.4 |
| June | 05:38 | 19:09 | 13h 30m | 13.6 |
| July | 05:48 | 19:11 | 13h 23m | 13.9 |
| August | 06:00 | 18:55 | 12h 55m | 13.8 |
| September | 06:10 | 18:27 | 12h 17m | 12.5 |
| October | 06:20 | 17:58 | 11h 39m | 10.1 |
| November | 06:36 | 17:40 | 11h 04m | 7.4 |
| December | 06:55 | 17:41 | 10h 46m | 6.0 |
Open water burns faster than a beach: the surface reflects sunlight up at you, and sunscreen washes off in the first few minutes. A long swim under a UV index above 6 needs a rash vest more than it needs more cream.
What the bands mean
| From | Description | In practice |
|---|---|---|
| above 26°C | Bath-like | Warm enough that it offers no cooling at all |
| above 22°C | Very comfortable | Swimwear, no time limit for most people |
| above 19°C | Comfortable | Pleasant once you are in; most people swim happily |
| above 16°C | Bracing | Swimmable but short; many prefer a shorty wetsuit |
| above 12°C | Cold | Wetsuit territory. Unprotected swims should be brief |
| below 12°C | Dangerous | Cold shock risk. Specialist gear and supervision |
Do you need a wetsuit in Shenzhen?
Some months, yes. The sea drops to 17.7°C in January. What thickness, month by month, for swimming and for surfing →
Other coastal cities in China
Where these numbers come from, and what they miss
- Open water, not your beach. The measurement is a satellite cell about 28 km across, centred 21.7 km from Shenzhen. Shallow bays and lagoons run warmer; exposed coasts with upwelling run colder, sometimes by several degrees.
- Surface temperature. Below a few metres the sea is often noticeably colder, and in summer a warm surface layer can sit over much colder water.
- A six-year average, not a thirty-year normal. Sea temperature varies little between years, so this is close — but it is not a climate normal, and any individual year will differ.
- Averages hide storms. A monthly mean says nothing about the week a cold current arrives.