Run early or late - Avoid running between 10am and 4pm as much as possible. If you have to run in the middle of the day, try to plan a shady route (woodland is ideal if possible). The coolest time of the day to run is first thing in the morning as roads have not had the opportunity to heat up by this time.
Hydrate fully prior to running - Drinking to thirst during a run is important, but being hydrated prior to training is also a fundamental part of success in the heat. A good way to measure your hydration levels is by monitoring your urine. If it's totally clear, you're drinking too much whereas if it's a dark colour like ice tea, you're definitely not taking enough fluids on board. The ideal colour is pale yellow.
Dress appropriately - Wear light coloured, loose fitting gear that allows moisture to pass through for evaporation. Stick to synthetic fabrics and steer well clear of cotton! Choose sunglasses that filter UVA and UVB rays and use waterproof sunscreen. A hat is advisable too to keep the sun out of your eyes, although please note this may lead to overheating, so a visor may be a better option if this has happened to you before.
Don't push it - It takes weeks for your body to adapt to the heat. So at first, rather than heading out at your usual speed, slow your pace to ensure that you get the distance in. You'll gradually get used to the higher temperatures, and as you do, you'll regain your pace. Another option is to initially go out without a watch so that you're not concerned about your speed at all, but you're spending time running in the heat and conditioning yourself to the weather.
Avoid over drinking water - When it's really hot outside it can be tempting to guzzle fluids prior to and during training. This however brings with it the risk of hyponatremia which occurs when there's either too much water or not enough sodium in your blood. It's a rare condition but can be extremely dangerous so be conscious of your fluid consumption in the heat. Consider a drink that contains electrolytes rather than all water.
Know the signs - Be familiar with the signs of heat problems. If you're out running and feel either faint, dizzy or disorientated, be sensible and stop! Also, if your skin becomes cold and clammy or you stop sweating, then take a break and find shade and fluid. A rule of thumb is to always have a means of communication with you on runs, and let someone know your route if possible.
By Marc Brown