#include <DHT.h>

#define DHTPIN 2
#define DHTTYPE DHT22
#define LEDPIN 8
DHT dht(DHTPIN, DHTTYPE );

float temperature;

void setup() {
  dht.begin();
  pinMode(LEDPIN, OUTPUT);
}

void loop() {
  temperature = dht.readTemperature();
  if (isnan(temperature)) {
    return;
  } else {
    if (temperature > 40) {
      digitalWrite(LEDPIN, HIGH);
      delay(1000);
      digitalWrite(LEDPIN, LOW);
    }
  }
  delay(1000);
}