I don't have direct experience with a child becoming so accustomed to sleeping with air conditioning that they were unable to sleep without it, but I know adults who have that problem, so I think it is a very real concern for you.
My suggestion is that during the two weeks leading up to your visits to your relatives without A.C., you gradually lower the amount of A.C. you use in your house (or at least the baby's room). The goal is to have the temperature as high as is safe for a day or two before the trip, with the gradual increase helping ease your child through the transition. That doesn't mean that you won't face some sleepless nights while visiting your relatives, but at least it gives you a better chance of your daughter falling asleep.
However, be very careful about making sure she does not overheat, either while you are gradually increasing the temperature at your home, or while visiting your relatives. Overheating is very dangerous to an infant.
Make sure you don't swaddle her when you have the temperature raised.
Check for warning signs frequently:
- Red pimples on the cheeks, neck, forehead, head, arms, or legs
- Damp hair (from sweat)
- Rapid breathing
- Flushed, red skin
- General restlessness
Some suggestions to help keep your baby comfortable while sleeping without air conditioning:
If you're going to be indoors, dress your infant in loose-fitting, lightweight garments, preferably made from a natural fiber like cotton, which absorbs perspiration better than synthetic fabrics. A good rule of thumb: "Dress the baby the way you're dressed," Dr. Epstein says. "If you're wearing shorts and a T-shirt, that will be fine for her too."
Since a baby doesn't perspire effectively, he can become overheated
far more quickly than an adult. That's why you should never leave an
infant in a hot room or a parked car. Even a few minutes could cause
his temperature to spike and, in extreme cases, may prove
Even if you don't see beads of sweat dripping from your infant's
forehead, he can be losing precious fluids to perspiration in hot
weather. A flushed face, skin that's warm to the touch, rapid
breathing, and restlessness may be warning signs of dehydration. Since
infants under 6 months shouldn't drink water (babies over 6 months can
take in modest amounts), replace the lost liquids by giving him extra
formula or by nursing more frequently. Babies should drink at least 50
percent more than usual in the summer (normal fluid intake is at least
two ounces per pound per day), so a ten-pound baby who usually takes
in 20 ounces should be offered a minimum of 30 ounces.