Spring: the most dangerous swim time

The weather's unseasonably warm, but the water is still winter-cold. While swimming in the sun is a treat to be sure, extra caution is needed. This is when most people get into trouble.

Outdoor swimming, especially winter swimming is wonderful. It's benefits for mind, body and spirit are there to be reaped by anyone and everyone with very few exceptions. For the most part, anyone can start swimming outdoors at almost any time of the year providing they take a few precautions. And those precautions are particularly important in the spring.

Spring time swim time

The weather warms up as our part of the earth rotates so that it's tilting closer to the sun. Being a tiny island our weather is variable as it's at the mercy of the wind direction. In a state of climate chaos, as we undoubtedly are, the weather's unpredictable to say the least. Where we were in the grips of the beast from the east last year, this year, we've got a heat wave.

In a way, swimming during snow storms is safer. When it's freezing outside, only hardy winter swimmers would even contemplate a dip. And those who do max out their dip time at a couple of breath-snatching minutes.

But when it's warm in early spring, even experienced winter swimmers get caught out. Lulled into a false sense of security by the warm sunshine, we stay in for too long and push ourselves too far, exposing ourselves to cold incapacitation. "Just being used to cold water swimming confers no immunity to its effects," posted experienced winter and Channel swimmer Andrew Wolf on Facebook. "Today the water was relatively warm at 7C and it was a sunny day. I went in and it felt colder than when I have swum at 3C or colder. However I got going, and felt OK. I swam 1k (20mins) but as I turned for the last leg at Clevedon marine lake I felt slightly unreal had tinnitus and was slightly concerned."

After Andy got out, he started shivering as usual and did everything he should to warm up - got dressed quickly and drank warm tea. But he then stopped shivering, and felt a reduction in his consciousness. "Never assume serious hypothermia will not happen, always ensure you swim with someone and limit your swim if you don't feel right," he said.

It's the water temperature that matters

As always, it's the water temperature that counts not the air temperature. After a winter dip, the sunshine will help you warm up, but it won't counter the effect of staying in the cold water for too long.

When you get into cold water, your blood vessels in your skin and extremities constrict. Warm blood goes to your core and the rest cools. When you get out again and start to warm up, the constricted blood vessels open up again and the cold blood mixes with the warm blood causing your overall core temperature to drop. This triggers the shiver response and is known as the afterdrop.

If you've got very cold in the water and then stimulate your blood vessels to open too quickly, it can deepen your afterdrop causing your core temperature to drop too fast and too low, which is why some people get taken ill after a winter swim. You can help prevent this by warming yourself gently - warm clothes, a warm drink. And by not staying in for too long in the first place.

Stay safe in the warm weather

So, even when the weather is gorgeous and it feels more like May than February, bear in mind that the water hasn't had time to warm up. It's still winter, and you should still swim like it's winter.

Most of all, it's not the time to for inexperienced outdoor swimmers to leap in. The contrast between the air and water temperature is greater and the cold water shock effect is a huge factor. I'm all for encouraging people to take the plunge, but nothing worries me more than the gangs of teenagers who come out in the sunshine and jump into frigid waters.

Wear your swim hats, wear your gloves and booties. Be aware of the water temperature and how long you should stay in. Be aware of how you feel: you should get out while you still feel comfortable. Take warming up seriously: stand in the sun, wrap up, put on your warm hat and cradle your cup of tea. Don't enter the water by jumping or diving in (you can swim and then jump in once your used).

Most of all, watch out for other swimmers and don't swim alone. It's a beautiful time of the year for swimming, so let's all do it safely so that we get the most from our winter dips.