I’ve been encouraged to suggest some energy-saving thoughts, but that’s not the priority at the moment. Just now, there’s too much heat….
Some of us are especially vulnerable - the very young, the very old, those compromised in various ways such as asthma - and there will be vulnerable friends and neighbours who might need some helpful guidance.
Many of us will NOT bother with the hydration advice - until significant symptoms are obvious. One thing I’ve learned from Services’ Survival Courses is that it’s not enough simply to replace the water. One also needs to replace the ‘salts’ excreted in sweat - especially little ‘uns and oldies. The best stuff for that is a product called ‘Dyarolyte’…. from most chemists. Just dissolve it in water. Several flavours….
Next, we’re not good at managing excessive heat. There’s much we could learn from other societies, ancient and modern, who have learned to deal with real heat. Think on this….
Most heat that comes from outside is 'radiated' in so block as much as you can. Mediterranean houses have sun-shutters and awnings for this purpose, while modern glass-wall office blocks have Reflective Coated triple glazing. Do what you can to achieve similar. Close curtains everywhere. Attach kitchen foil with sellotape inside windows on sunny side and where facing sun-heated brick walls - which re-radiate heat. A lot.
Borrow ideas from the Arabian and Persian civilisations.... they used both convective and evaporative cooling, passively, to cool their shaded interiors over many centuries. Heated air rises in a house unless it is trapped upstairs, so open a venting pathway at the top of the cooler side of the house - windows opened top/sides a few inches, curtains and doors slightly ajar - and provide for its replacement low down.... ideally from a cool damp cellar or from a shaded dampened courtyard, which is the way 'wind towers' worked for thousands of years - and still do - without electricity.
Hotel and public buildings atriums in hot countries have pools and splashing fountains of cool water. These cool the atmosphere considerably. We can emulate some of that by placing a wire/wood drying rack above a large bowl of cold water, and dangling some towels down into the water. This creates a 'wicking', and air flowing over the damp towels/bed sheets is cooled by evaporative cooling. Enhance that air flow by positioning a small electric fan to encourage such airflow ( careful - electrical safety! ) near the damp towel-tower and possibly also up near the warmer-air outlet upstairs.
That'll be a bit less effective in a modern British bungalow but, of course, a 'true' bungalow had shaded verandahs all round and a punkah wallah or two to create the through-draught..... which wouldn't be easy or PC to arrange today!
That's what was done on the airbase I worked on deep in the Omani desert circa 79/80 when the fitted AC units failed; it's largely what I've done here..... and the ground floor of this house is half-a dozen Degrees C cooler than the bedrooms upstairs.