Hola me podrías ayudar, lo compilo y me tira  estos errores

sketch_may17b.ino:11:17: error: DHT.h: No such file or directory
sketch_may17b.ino: In function 'void setup()':
sketch_may17b:29: error: 'dht' was not declared in this scope
sketch_may17b.ino: In function 'float getTemperature()':
sketch_may17b:59: error: 'dht' was not declared in this scope
sketch_may17b.ino: In function 'float getHumidity()':
sketch_may17b:62: error: 'dht' was not declared in this scope