It would depends on the region that you are in, some places are more extremes than others. At least in my country this never happens as we are in the middle of the world the weather is always predictable. Nevertheless if I had to prepare for extraen weather I would have some clothes, creams (sunscreen and regular ones), also I’d adapt my house depending on the climate if it is too cool I would have a fan or if it is too hot I would have heater.