Most houseplants are happy at the same temperatures as humans. Thats how they became popular as indoor plants. They even enjoy a slight dip in the temperature in the evening. What they often cant handle is exposure to cold drafts. Placing an indoor plant, especially a tropical or blooming plant, near a frequently opened door to the outside or too close to a window with limited insulation will have the same effect as leaving the plant unprotected outside. You will probably first notice leaves dropping and the plant may look like it needs water, when actually it needs warmth. Repeated or prolonged exposure to cold temperatures will kill a houseplant.