ESP32-Based OpenWeather API Weather Station

With the rise of IoT applications, building a weather station using an ESP32 microcontroller is both practical and exciting. By leveraging OpenWeather's API, we can fetch real-time weather data and display it on the terminal. This project is perfect for beginners and experienced IoT and embedded systems developers.

Materials Required

Before starting, ensure you have the following components:

• ESP32 Development Board

Setting Up OpenWeather API

• Create an account on OpenWeather (OpenWeather Website).

• Generate an API Key to retrieve weather data.
• Choose API Endpoints (Current weather or forecast) and note the required JSON format

Installing Required Libraries

To handle API responses and display weather data, install the following libraries in the Arduino IDE:

• ArduinoJson for parsing JSON data.
• WiFiClientSecure for secure HTTPS communication.

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ESP32 Code for Fetching Weather Data

Below is the ESP32 Arduino Sketch to retrieve weather data and display it via a serial terminal:

#include <WiFi.h>
#include <HTTPClient.h>
#include <Arduino_JSON.h>

const char* ssid = "";
const char* password = "";

// Your Domain name with URL path or IP address with path
String openWeatherMapApiKey = "";

// Replace with your country code and city
String city = "Coimbatore";
String countryCode = "IN";

// THE DEFAULT TIMER IS SET TO 10 SECONDS FOR TESTING PURPOSES
// For a final application, check the API call limits per hour/minute to avoid getting blocked/banned
unsigned long lastTime = 0;
// Timer set to 10 minutes (600000)
//unsigned long timerDelay = 600000;
// Set timer to 10 seconds (10000)
unsigned long timerDelay = 10000;

String jsonBuffer;

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

  WiFi.begin(ssid, password);
  Serial.println("Connecting");
  while(WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.print("Connected to WiFi network with IP Address: ");
  Serial.println(WiFi.localIP());
 
  Serial.println("Timer set to 10 seconds (timerDelay variable), it will take 10 seconds before publishing the first reading.");
}

void loop() {
  // Send an HTTP GET request
  if ((millis() - lastTime) > timerDelay) {
    // Check WiFi connection status
    if(WiFi.status()== WL_CONNECTED){
      String serverPath = "http://api.openweathermap.org/data/2.5/weather?q=" + city + "," + countryCode + "&APPID=" + openWeatherMapApiKey;
      
      jsonBuffer = httpGETRequest(serverPath.c_str());
      Serial.println(jsonBuffer);
      JSONVar myObject = JSON.parse(jsonBuffer);
  
      // JSON.typeof(jsonVar) can be used to get the type of the var
      if (JSON.typeof(myObject) == "undefined") {
        Serial.println("Parsing input failed!");
        return;
      }
    
      Serial.print("JSON object = ");
      Serial.println(myObject);
      Serial.print("Temperature: ");
      double a = myObject["main"]["temp"];
      Serial.println(a/10);
      Serial.print("Pressure: ");
      Serial.println(myObject["main"]["pressure"]);
      Serial.print("Humidity: ");
      Serial.println(myObject["main"]["humidity"]);
      Serial.print("Wind Speed: ");
      Serial.println(myObject["wind"]["speed"]);
    }
    else {
      Serial.println("WiFi Disconnected");
    }
    lastTime = millis();
  }
}

String httpGETRequest(const char* serverName) {
  WiFiClient client;
  HTTPClient http;
    
  // Your Domain name with URL path or IP address with path
  http.begin(client, serverName);
  
  // Send HTTP POST request
  int httpResponseCode = http.GET();
  
  String payload = "{}"; 
  
  if (httpResponseCode>0) {
    Serial.print("HTTP Response code: ");
    Serial.println(httpResponseCode);
    payload = http.getString();
  }
  else {
    Serial.print("Error code: ");
    Serial.println(httpResponseCode);
  }
  // Free resources
  http.end();

  return payload;
}

Upload and Monitor:

Finally, connect the ESP32 to the system and select the correct port and the board, then upload the sketch.

Explanation

• ESP32 connects to WiFi and sends an HTTPS request to OpenWeather API.
• The response is in JSON format, parsed using ArduinoJson.
• The ESP32 extracts key weather details (temperature & condition).

Optional Enhancements

• Forecast Data: Modify the API request to fetch a 5-day forecast.
• Web Server Dashboard: Convert ESP32 into a WiFi server to display weather in a browser.
• Store API Data: Log weather readings to Firebase for historical tracking.

Conclusion

This ESP32-based OpenWeather API weather station allows real-time data retrieval with minimal hardware. Whether for home automation or IoT learning, this project is a great way to integrate API-based data retrieval into embedded systems.