Negative Temperature and Humidity with DHT11 and DS18B20 with MQ-137/MQ135 on ESP8266

FYI, DHT11 doesn’t do negative values. But the DHT12 will, and higher resolution as well.

I also use a BME280 - I2C based Temperature, Humidity and Barometric sensor that is even better then the DHT12

Some of my code with that one is in this Topic - Weather Station with ESP32 (with OLED), Nextion & BME280 (and now Virtuino)