ESP8266 Weather Forecaster

In this post you’re going to build a weather forecaster with an ESP8266.

I hate being out on a rainy day without an umbrella and I’m pretty sure it’s the same for everyone else.

Often, the weather widget on our smartphones displays the weather forecast but when you’re in a hurry you forget to pay attention to it.

So, it would be nice to have a device hanging at the back of the door which reminds you to leave your house with an umbrella on a day where it might rain. This device tells you the weather forecast with a change in the LED color. This device wouldn’t have an alarm neither a screen, just a few LEDs that would fit naturally into your environment.

Parts required

Here’s a complete list of the components you need for this project (click the links below to find the best price at Maker Advisor):

  • ESP8266 12-E – read Best ESP8266 Wi-Fi Development Boards
  • 4x LEDs (different colors to represent different weather conditions)
  • 4x Resistors (220 or 330 ohms should do the trick)
  • Breadboard
  • Jumper wires

Open Weather Map

This project is based on the Open Weather Map API, so it’s necessary to sign up on their platform and obtain an API key before we get down to putting together the schematics and writing the code.

OpenWeatherMap’s free plan provides everything you need for thins example. To use the API you need an API key, known as the APIID. To get an APIID:

  1. Open a browser and go to OpenWeatherMap
  2. Press the Sign up button and create a free account
  3. Once your account is created, you’ll be presented with a dashboard that contains several tabs (see figure below)
  4. Select the API Keys tab and copy your unique Key

This is a unique key you need to pull information from the site. Copy and paste this key somewhere, you’ll need it in a moment.

To pull information on weather in your chosen location, enter the following URL with the sections in curly brackets replaced with your chosen location information and your unique API key:{your city},{your country code}&APPID={your API Key}&mode=json&units=metric&cnt=2

Replace {your city} with the city you want data for, {your country code} with the country code for that city, and {your API key} with your unique API key we found previously. For example, our API URL for the town of Porto in Portugal, after replacing with the details, would be:,PT&APPID=801d2603e9f2e1c70e042e4------&mode=json&units=metric&cnt=2

Note: more information on using the API to get weather information is available here.

Copy your URL into your browser and it should give you a bunch of information that corresponds to your local weather forecast information.

Keep your unique API key safe and we can then move to the code section.

Installing the ArduinoJson library

For this project you need to install the ArduinoJson library in your Arduino IDE that allows you to Decode and Encode JSON with Arduino or ESP8266. Follow these next steps:

  1. Click here to download the ArduinoJson. You should have a .zip folder in your Downloads folder
  2. Unzip the .zip folder and you should get ArduinoJson-master folder
  3. Rename your folder from ArduinoJson-master to ArduinoJson
  4. Move the ArduinoJson folder to your Arduino IDE installation libraries folder
  5. Finally, re-open your Arduino IDE

Uploading code

Having the ESP8266 add-on for the Arduino IDE installed (how to Install the ESP8266 Board in Arduino IDE), go to Tools and select “NodeMCU (ESP-12E Module)”.

Copy the following code to your Arduino IDE and upload it to your ESP8266 board.

Go through the code to add your SSID, password, city, country code and Open Weather Map API key.

  * Author: Emmanuel Odunlade 

#include <ArduinoJson.h>
#include <ESP8266WiFi.h>
#include <WiFiClient.h>

// Replace with your SSID and password details
char ssid[] = "REPLACE_WITH_YOUR_SSID";        
char pass[] = "REPLACE_WITH_YOUR_PASSWORD";   

WiFiClient client;

// Open Weather Map API server name
const char server[] = "";

// Replace the next line to match your city and 2 letter country code
// How your nameOfCity variable would look like for Lagos on Nigeria
//String nameOfCity = "Lagos,NG"; 

// Replace the next line with your API Key

String text;

int jsonend = 0;
boolean startJson = false;
int status = WL_IDLE_STATUS;

int rainLed = 2;  // Indicates rain
int clearLed = 3; // Indicates clear sky or sunny
int snowLed = 4;  // Indicates snow
int hailLed = 5;  // Indicates hail


unsigned long lastConnectionTime = 10 * 60 * 1000;     // last time you connected to the server, in milliseconds
const unsigned long postInterval = 10 * 60 * 1000;  // posting interval of 10 minutes  (10L * 1000L; 10 seconds delay for testing)

void setup() {
  pinMode(clearLed, OUTPUT);
  pinMode(rainLed, OUTPUT);
  pinMode(snowLed, OUTPUT);
  pinMode(hailLed, OUTPUT);
  while (WiFi.status() != WL_CONNECTED) {
  Serial.println("WiFi Connected");

void loop() { 
  //OWM requires 10mins between request intervals
  //check if 10mins has passed then conect again and pull
  if (millis() - lastConnectionTime > postInterval) {
    // note the time that the connection was made:
    lastConnectionTime = millis();

// print Wifi status
void printWiFiStatus() {
  // print the SSID of the network you're attached to:
  Serial.print("SSID: ");

  // print your WiFi shield's IP address:
  IPAddress ip = WiFi.localIP();
  Serial.print("IP Address: ");

  // print the received signal strength:
  long rssi = WiFi.RSSI();
  Serial.print("signal strength (RSSI):");
  Serial.println(" dBm");

// to request data from OWM
void makehttpRequest() {
  // close any connection before send a new request to allow client make connection to server

  // if there's a successful connection:
  if (client.connect(server, 80)) {
    // Serial.println("connecting...");
    // send the HTTP PUT request:
    client.println("GET /data/2.5/forecast?q=" + nameOfCity + "&APPID=" + apiKey + "&mode=json&units=metric&cnt=2 HTTP/1.1");
    client.println("User-Agent: ArduinoWiFi/1.1");
    client.println("Connection: close");
    unsigned long timeout = millis();
    while (client.available() == 0) {
      if (millis() - timeout > 5000) {
        Serial.println(">>> Client Timeout !");
    char c = 0;
    while (client.available()) {
      c =;
      // since json contains equal number of open and close curly brackets, this means we can determine when a json is completely received  by counting
      // the open and close occurences,
      if (c == '{') {
        startJson = true;         // set startJson true to indicate json message has started
      if (c == '}') {
      if (startJson == true) {
        text += c;
      // if jsonend = 0 then we have have received equal number of curly braces 
      if (jsonend == 0 && startJson == true) {
        parseJson(text.c_str());  // parse c string text in parseJson function
        text = "";                // clear text string for the next time
        startJson = false;        // set startJson to false to indicate that a new message has not yet started
  else {
    // if no connction was made:
    Serial.println("connection failed");

//to parse json data recieved from OWM
void parseJson(const char * jsonString) {
  //StaticJsonBuffer<4000> jsonBuffer;
  DynamicJsonBuffer jsonBuffer(bufferSize);

  JsonObject& root = jsonBuffer.parseObject(jsonString);
  if (!root.success()) {
    Serial.println("parseObject() failed");

  JsonArray& list = root["list"];
  JsonObject& nowT = list[0];
  JsonObject& later = list[1];

  // including temperature and humidity for those who may wish to hack it in
  String city = root["city"]["name"];
  float tempNow = nowT["main"]["temp"];
  float humidityNow = nowT["main"]["humidity"];
  String weatherNow = nowT["weather"][0]["description"];

  float tempLater = later["main"]["temp"];
  float humidityLater = later["main"]["humidity"];
  String weatherLater = later["weather"][0]["description"];

  // checking for four main weather possibilities
  diffDataAction(weatherNow, weatherLater, "clear");
  diffDataAction(weatherNow, weatherLater, "rain");
  diffDataAction(weatherNow, weatherLater, "snow");
  diffDataAction(weatherNow, weatherLater, "hail");

//representing the data
void diffDataAction(String nowT, String later, String weatherType) {
  int indexNow = nowT.indexOf(weatherType);
  int indexLater = later.indexOf(weatherType);
  // if weather type = rain, if the current weather does not contain the weather type and the later message does, send notification
  if (weatherType == "rain") { 
    if (indexNow == -1 && indexLater != -1) {
      Serial.println("Oh no! It is going to " + weatherType + " later! Predicted " + later);
  // for snow
  else if (weatherType == "snow") {
    if (indexNow == -1 && indexLater != -1) {
      Serial.println("Oh no! It is going to " + weatherType + " later! Predicted " + later);
  // can't remember last time I saw hail anywhere but just in case
  else if (weatherType == "hail") { 
   if (indexNow == -1 && indexLater != -1) {
      Serial.println("Oh no! It is going to " + weatherType + " later! Predicted " + later);

  // for clear sky, if the current weather does not contain the word clear and the later message does, send notification that it will be sunny later
  else {
    if (indexNow == -1 && indexLater != -1) {
      Serial.println("It is going to be sunny later! Predicted " + later);


Wire your circuit accordingly to the schematic below:


The next figure describes what each LED indicates: (D2) Rain, (D3) Clear sky, (D4) Snow and (D5) Hail:

Here’s a photo of the final circuit:

Wrapping up

Nowadays, the goal of computing is to create a natural user interface between man and computers. We are looking to things like AR (Augmented Reality) to make that reality, but the truth is we are all getting tired of constantly looking at our phones and PCs for the tiniest piece of information.

I think having this project hanged somewhere around the house where you can easily know the weather on your way out is extremely useful.

To take this project further, I may throw in a 3D printed enclosure with a battery back up to make this look more neat. I will certainly share with you when that is done.

Thanks for reading!

Published by Gnd_To_Vcc

Here to spread my knowledge . Knowledge should always be spread not stored.

7 thoughts on “ESP8266 Weather Forecaster

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