What temperature and shade does orchid need and can it be grown in warm plains?

It depends on the orchid type. Dendrobium tolerates warm humid conditions and is the one usually grown in warmer plains under shade net with high humidity, so a warm plains district can suit Dendrobium if you provide shade, humidity through misting or a fan and pad, and good air movement. Cymbidium on the other hand needs cool hill conditions and will not perform in warm plains. Orchids want bright diffused light, not direct harsh sun, so roughly heavy shade through net is used, and they hate both drying out and waterlogging at the roots. So Dendrobium yes with the right protected setup and humidity, Cymbidium no in your climate. Confirm the exact shade percentage and humidity target for your chosen variety and your local temperatures with a floriculture specialist or your horticulture department before building.