It is a common misconception or overthought that we only become dehydrated in the hot summer months of the year. Yes the increased perspiration that occurs in order to cool us down can increase our fluid losses, but the compensatory thirst mechanism is more exaggerated meaning we drink more. However, in the winter months when it is colder and we sweat less i.e. lose less electrolyte, we tend not to drink so much partly because we don’t have a strong thirst reflex because of relative electrolyte balance, but also because we don’t feel the need to drink so much when it is cooler.
The problem is this, we do still perspire in cooler environments, plus many of us are in centrally heated offices or working manual jobs that still makes us perspire and lose fluid via other ways too including urination, excretion and breathing. It is therefore all too common for people to be sat at a desk, or out in a blustery building site (for example) and be chronically dehydrated (dehydrated over days and even weeks). In order to minimise this it is good practice to sometimes consume an isotonic beverage as well as regular tea, coffee and water. The reason for this is to deliver solute in the form of sodium, potassium, chloride etc, these electrolytes not only enhance rehydration but also stimulate thirst, encouraging you to drink more. Win win!