Make a Raspberry Pi weather station with the BME280

Level: Beginner  ·  Time: 30 minutes  ·  Board: any Raspberry Pi with a 40-pin header

The BME280 measures temperature, humidity and barometric pressure, the three basics of a weather station. It talks over I2C, so it needs just four wires and no soldering if you use STEMMA QT cables.

What you need

• Raspberry Pi Zero 2 W – or any Pi with a 40-pin header
• Adafruit BME280 sensor
• Female/female jumper wires
• 0.91" OLED display – optional, for a live readout

1. Wire it up

Tip: Keep the sensor a few inches away from the Pi on its wires. The Pi's own heat will otherwise push the temperature reading up.

2. Turn on I2C and find the sensor

sudo raspi-config nonint do_i2c 0
sudo apt install -y i2c-tools
i2cdetect -y 1

You should see 77 in the grid, which is the BME280's default address.

3. Install the library

Raspberry Pi OS asks you to install Python packages in a virtual environment:

python3 -m venv ~/weather --system-site-packages
source ~/weather/bin/activate
pip install adafruit-circuitpython-bme280

4. Read the sensor

Save this as weather.py:

import csv, time
from datetime import datetime
import board
from adafruit_bme280 import basic as adafruit_bme280

i2c = board.I2C()
bme = adafruit_bme280.Adafruit_BME280_I2C(i2c)
bme.sea_level_pressure = 1013.25   # set to your local value for accurate altitude

with open("weather.csv", "a", newline="") as f:
    log = csv.writer(f)
    while True:
        row = [datetime.now().isoformat(timespec="seconds"),
               round(bme.temperature, 1),
               round(bme.relative_humidity, 1),
               round(bme.pressure, 1)]
        print(f"{row[1]} °C  {row[2]} %RH  {row[3]} hPa")
        log.writerow(row)
        f.flush()
        time.sleep(60)

python weather.py

You'll get a reading every minute on screen and in weather.csv, which opens straight into a spreadsheet for graphs.

5. Run it automatically

To start logging at boot, add a line to your crontab (crontab -e):

@reboot cd /home/yourname && /home/yourname/weather/bin/python weather.py

Ideas to take it further

• Add the OLED display for a desk readout. It shares the same I2C pins.
• Add a SCD-40 to track CO₂ and know when to open a window.
• Publish the readings to Home Assistant over MQTT.