Use old 433MHz outdoor temperature/humidity sensors, hack their encoding, add a display and finally connect it to the internet.

External temperature and/or humidity sensors, available from cheap weather stations, are sending temperature and humidity in various protocols via 433MHz. Use the sensors, hack the protocols, and then collect the data and use it for display of the current weather. If additional sensors for pressure are provided (e.g. BME280) also a local weatherforecast is possible. Connect all the data and use a cloud service to show a trending.