Checking the sensor data on your smartphone

Technically speaking, there are three options how you can view your sensor data on your smartphone. The most simple solution would be to run a webserver on the ESP module. This would require the module to be active all the time, waiting for you to request current weather data. This solution makes it impossible to use batteries for more than a couple of hours.
The second option is to let the ESP-module send the data to a private webserver in your local network. This server would receive weather data periodically from the ESP module and presents it to the smartphone user. This webserver can run on Linux or Windows PCs. Obviously, this server needs to run 24/7 so it can serve your requests any time you want to check the weather.
The third option, and that’s the one you should go for, is the IoT cloud. There a numerous IoT cloud providers which allow the ESP module to send the sensor data to their servers and visualize / analyze your data for display on your smartphone. The only prerequisite is to create an account at a provider of your choice and configure / setup the sensor endpoints. The ESP module’s code needs to be adjusted for sending sensor data to your private IoT cloud service.