Building a Backyard Weather Station for Under €80
I've been a casual weather watcher since childhood — my grandfather had a mercury barometer in his hallway that I checked obsessively every visit. When I finally had my own space, I wanted a proper instrument setup, but the commercial stations with data logging cost €300-800. So I built one for €76.
The core: a Raspberry Pi Zero 2W (€18), a BME280 sensor for temperature/humidity/pressure (€4), and a reed switch anemometer salvaged from a broken Davis station I found at a market (€8). The Pi logs readings every 60 seconds to a SQLite database and serves a minimal web interface on the local network.
The tricky part was placement. The BME280 needs to be shielded from direct sunlight and rain but still exposed to free airflow. I made a radiation shield from two white plastic plates — essentially a miniature Stevenson screen. Without it, readings on sunny afternoons were running 3-4°C high.
Pressure calibration: altitude compensation is essential. My house is at 87m above sea level, which means the raw sea-level-equivalent pressure is about 10.3 hPa higher than the sensor reading. Most weather apps report sea-level pressure, so I apply: P_sea = P_sensor × exp(altitude / (temperature_kelvin × 29.3)).
After 14 months running, the system has logged 612,000 readings and missed about 40 minutes of data due to a single SD card hiccup. Not bad for €76.