We just designed an ESPwatch with weather forecasting, with MQTT and Openweathermap.
It based on the ESP12 and 12864 OLED, get the real time from MQTT, and 3~5 days weather forecasting, depends on the city you lived.
Although the whole product is not difficult, but i think it useful for the learner to learn the basic hardware and coding, about IOT. i have post the detailed step-by-step guide at:ESPwatch guide
The most difficult for the learners is the Arduino IDE library installing..wish the very detailed guide helpful. All the hardware& software are open source at:ESPwatch open-source hardware&software