The first reading

// The first reading: temperature and humidity, every two seconds.
//
// Wiring, sensor to board:
//   Sensor GND  -> board GND
//   Sensor VCC  -> board 5V on an Uno, 3V3 on an ESP32, ESP32-S3 or Pico
//   Sensor NC   -> nothing. It is connected to nothing on the board either.
//   Sensor DATA -> Uno D2, ESP32 GPIO 18, ESP32-S3 GPIO 4, Pico GP2
//
// Count the pins from the square pad: GND, VCC, NC, DATA.
//
// Arduino IDE: install "DHT sensor library" by Adafruit from the Library
// Manager (Tools -> Manage Libraries, search DHT sensor library). When it
// offers to install "Adafruit Unified Sensor" as well, say yes -- it will
// not compile without it. No special Tools settings on any of these boards.

#include <DHT.h>

#define DHT_PIN  2      // Uno D2.  ESP32: 18.  ESP32-S3: 4.  Pico: 2.
#define DHT_TYPE DHT22  // DHT22 for the white cage, DHT11 for the blue one.

DHT dht(DHT_PIN, DHT_TYPE);

void setup() {
  Serial.begin(115200);
  dht.begin();
}

void loop() {
  // Humidity first, then temperature. The second call does not touch the
  // wire: the library caches for two seconds, so both numbers come out of
  // the same reading rather than out of two readings a millisecond apart.
  float humidity = dht.readHumidity();
  float celsius  = dht.readTemperature();

  // A failed read returns nan rather than throwing, and nan prints as "nan"
  // and compares false against everything. Checking is not optional: one
  // failure in a hundred is normal for this protocol.
  if (isnan(humidity) || isnan(celsius)) {
    Serial.println("read failed");
  } else {
    Serial.print(celsius);  Serial.print(" C  ");
    Serial.print(humidity); Serial.println(" %");
  }

  delay(2000);   // The floor is 2 s for a DHT22, and 2 s in this library
}                // for a DHT11 too. Asking faster returns the old value.