New episodes will be released on Wednesdays, but if you’re in the UK, listen to new episodes, a week early, first on BBC Sounds: bbc.in/3zqa6BB Get that brolly out! It may feel deeply counter-intuitive - but rainy days could offer a host of health and mood-lifting benefits. Rain improves air quality, literally washing fine particulate pollution away, and rainfall also releases Geosmin, a fragrant compound which is linked with relaxation and increased serotonin levels. What’s more, Professor Michael Terman, from Columbia University in New York, introduces Michael to negative air ions created after rainfall. He is researching how high levels of negative ions could potentially reduce stress, stave off depression and maybe even boost your immune system. Meanwhile, our volunteer Dennis steps outside and embraces the rain. Michael Mosley ventures to his local pool and the sea to explore the unique benefits of going for a swim - from improving memory and mental agility, to boosting longevity. Professor Hirofumi Tanaka, from the University of Texas at Austin, reveals why water-based exercises like swimming are especially good for improving the elasticity of your blood vessels and a new way to exercise in the pool. There really seems to be something special about being in the water that can help your heart, improve joint pain and even boost your brain. Surprisingly, water-based exercise can be more beneficial than land-based exercises!