One little project and you're hooked! You know you're going to want another sensor in the yard, so consider a gateway running MQTT (called a broker). Once you have that, it's really easy to add more sensors.
But if you're really strong willed an will only be using two devices ever, you might look at https://nrf24.github.io/RF24/index.html. You can get an Arduino Nano and an nRF24 radio for about $3.50 from Aliexpress (downside: delivery takes ~2 months, so get 10 each.)
MySensors Library can do this, too, but I find it a little bloated.
Personal note: I'm 70, retired engineer, and have only four projects going right now.
