The sun is shining and this feels me with joy. But, like many of us, I am working from home so no air con, and my desk is just under the roof with a skylight just above my head. I can feel that I am getting dehydrated by the minutes!
Signs of dehydration?
Thirst and dry mouth of course, but not only. Soon I will feel tired, will struggle to concentrate, I will definitely get irritable with a headache. I might even feel dizzy. 
(Notes: if that sounds a bit like a hang-over it is because this is exactly what is going on after a heavy night - we are dehydrated as well as being intoxicated. To alleviate those symptoms, check out my rehydration drink recipe at the bottom of this article)
And one issue I have is that I always seems to feel thirst slightly too late. Turns out I am not the only one. Thirst is is well known for being an unreliable tool to signal dehydration and ensure full re-hydration  .
Why does good hydration matter?
The obvious function of water is to enables body temperature regulation through the process of sweating. But it goes way beyond that.
It facilitates digestion - dissolving nutrients for absorption and preventing from constipation.
It plays a crucial part in the detoxification process, eliminating waste products and toxins through urine.
It provides the perfect environment for metabolic reactions and cells signal exchange so our organs can function and communicate with each others.
It act as a lubricant for our joints and eyes. 
Pretty useful stuff, you will all agree.
How much should we drink?
Needs will vary from one person to another based on many factors such as age, muscle mass, climate, diet and physical activity. But in average, adults needs between 1.5 to 2L of fluid a day. 
The best tool to check our level of hydration is to look at the colour of our urine. Pale yellow or straw you are fine, Anything darker and you could do with more fluid 
Use prompt - have always a glass or a bottle of water near by to remind yourself to drink.
Prefer water rather than soft drinks as these can be bad for your teeth and be unnecessarily calorie-heavy.
If you find drinking water no so appealing, jazz it up a bit.
Jazz your water up
Make ice tea - for example make a fresh mint tea (infuse 6 leaves in boiling water) and let it cool down before popping it into the fridge.
Fruit flavouring - chop a couple of strawberries, a zest of lime, a slice of orange, bits of cucumber and add to the water.
Herb flavouring - you can use mint but try others such as basil, fresh thyme, lemon verbena, juniper berries.
Home-made squash - squeeze an orange and dilute it with water (1:3 ratio)
Recipe - re-hydration drink for pre-, post- and in-exercise
Simply mix together
500ml fruit juice
 Jéquier, E., Constant, F. 2010. Water as an essential nutrient: the physiological basis of hydration. Eur J Clin Nutr 64, 115–123. https://doi.org/10.1038/ejcn.2009.111
 Adolph, E.F., 1947. Physiology of Man in the Desert. Physiology of Man in the Desert.
Millard-Stafford M, Wendland DM, O'Dea NK, Norman TL. 2012. Thirst and hydration status in everyday life. Nutr Rev.;70 Suppl 2:S147‐S151. https://doi.org/10.1111/j.1753-4887.2012.00527.x