Does the area have WiFi?
One approach is to use ESP8266 boards with a BME280 temperature/pressure/humidity sensor.
The firmware on the ESP can be Arduino, Tasmota, or ESPHome / ESPEasy.
A bare ESP is cheapest but development boards are the easiest to setup because they have USB power and data interface.
Or ESP32 boards (a bit more expensive) can apparently run Node-red https://discourse.nodered.org/t/anybody-experimenting-with-node-red-mcu/71836.
ESPs are low power and have deep sleep so you could run one for months off a battery.
For communicating to Node-red, as always, MQTT. You probably want your own Mosquitto MQTT server.
Edit: Just a note to say that I have been trying to get BME280s working on a couple of ESP8266s with Tasmota today.
The Wemos D1 mini said there was insufficient space to install the right version of Tasmota, the other one doesn't seem to recognise the BME280.
So it's not totally straightforward!
