If you do not have a greenhouse or a conservatory, place orchids on a windowsill. If you see that the leaves are reddening at the edges or have become pale and yellow, the orchid is getting too much light. Move it to a shadier spot. You will know when the level of light is good because the orchid's leaves will stay glossy and green. During the summer months, keep orchids outside in indirect sun. Remember to water them regularly, and occasionally feed them with an orchid fertilizer.
Orchids thrive in a humid atmosphere and they must have excellent ventilation around their roots. Never re-pot your orchid in regular soil---you need a special orchid mix and special pots with air vents. If you live in a dry climate, it will help to sit your orchids on a tray of pebbles. Keep a shallow layer of water around the pebbles, but make sure the orchid's roots are never submerged. The water moistens the air around the orchid. To replicate humid conditions, spritz the orchid with water regularly.
Orchids generally can not tolerate temperatures lower than 50 degrees. If your orchids are kept outside during warmer months, wait until nighttime temperatures have dropped into the 50s, as the colder air promotes the growth of new stems and blooms. Because orchids thrive in temperatures up to around 85 degrees, in most climates it is unlikely to become too hot for them indoors. When temperatures are high, increase the amount and frequency of watering. In hot climates, look for heat-tolerant orchids like Phalaenopsis and Dendrobium.