have you seen this thread ?
https://www.theguineapigforum.co.uk/threads/hot-weather-management-and-heat-strokes.105317/
This is a section of it ...
What you can do during a heat wave:
- keep your piggies out of full sun at all times. If they are on the lawn (preferably not during the hottest hours) or in a hot indoors room, place wet towels or fleece over the run or cage and keep these damp. The evaporating water will cool the surrounding air.
- move your indoors guinea pigs to the coolest room in your house. Air this room as much as safely possible during the cooler hours between late afternoon/evening until early morning, so you can get it as cool as possible; run a fan near window to help bring the cooler air inside.
During the hottest hours of the day, please close any windows and draw your curtains where the sun is going to shine on to keep the room cooler than outdoors. If you are at home, you can close and open windows as the sun moves round; if you are out working, please consider which windows are impacted.
If you can, turn on your air conditioning or a fan, but please do not blast your guinea pigs with it directly.
Do not open all your windows wide with a fan running on full on very hot day - all you do, is to encourage the even hotter outdoors air inside!
- move the hutch away from full sun and hot patios that throw the heat around. If that is not possible, move the piggies out of a hutch or hot shed to a cooler place for the duration of the heat wave.
- wrap a frozen bottle of water in a towel or a sock or use freezable gel cool bags or pods instead.
You can also improvise with cool bag freezer blocs if you have those or even by putting your microwaveable snugglesafe heat pads in the fridge (NOT the freezer!).
Please remember to leave room for the ice to expand when putting a water filled plastic bottle into the freezer, or you will get soaked bedding!
- place a ceramic tile in their cage/hutch for them to suck heat from their body.
- Wiping your piggies gently down with a cool but not ice cold damp rag can also help to lower the temperature in a guinea pig that is suffering in the heat. Don't cold-shock overheated animals to prevent cardiac arrest.
- feed more watery veg like cucumber, chopped celery sticks, lettuce or melon, but please don't overdo it; too much can cause diarrhea!
- make sure that they have access to fresh, cool water at all times. You can use ice cubes or crushed ice if you are away during the heat of the day and need the water to stay cool for as long as possible. Sippy water bottles that open at the top will allow that.
Otherwise, please refresh the water regularly. Keep any water bottles out of full sun.
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Please DO NOT feed frozen treats! Piggies can badly injure their lips and tongues when nibbling to eagerly!
- give long-haired pet piggies a short haircut or at least cut the back and sides short and only leave a thin long top layer for show! They will feel a lot perkier without wearing the equivalent of skiing gear on a tropical beach. Their coats will grow back again for the cooler autumn and winter!