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Desktop Weather Station

Works with

Any CircuitPython board with I2C — Feather M0/M4, ItsyBitsy, QT Py, Trinket M0, RP2040 boards

Libraries used: adafruit_bme280 · adafruit_displayio_ssd1306 · adafruit_display_text

What you will build

A compact desk gadget that reads temperature, humidity, and barometric pressure from a BME280 sensor, calculates a "feels like" heat index, and displays all four values on a crisp OLED screen. The display refreshes every five seconds. Leave it running on your desk and you will have a real-time microclimate snapshot of wherever you are building.

Both the BME280 and the SSD1306 OLED share the same two-wire I2C bus — no extra wiring complexity, just daisy-chain them with STEMMA QT cables or a short breadboard run.

Parts list

Part Notes
CircuitPython board with I2C Any board works
BME280 temperature / humidity / pressure breakout Adafruit #2652
SSD1306 OLED display, 128×64 Adafruit #326 or #938
STEMMA QT cables (×2) or breadboard jumpers I2C daisy-chain
USB cable + power source

Wiring

graph TD
    MCU["CircuitPython Board"]
    BME["BME280\nTemp / Humidity / Pressure"]
    OLED["SSD1306 OLED\n128x64"]

    MCU -- "3.3V" --> BME
    MCU -- "GND" --> BME
    MCU -- "SCL" --> BME
    MCU -- "SDA" --> BME

    BME -- "SCL (daisy-chain)" --> OLED
    BME -- "SDA (daisy-chain)" --> OLED
    MCU -- "3.3V" --> OLED
    MCU -- "GND" --> OLED

Tip

The BME280 defaults to I2C address 0x77. The SSD1306 defaults to 0x3C. They coexist on the same bus without any configuration changes.

Complete code

import time
import board
import busio
import displayio
import terminalio
import adafruit_bme280.basic as adafruit_bme280
import adafruit_displayio_ssd1306
from adafruit_display_text import label

# --- Release any previous display ---
displayio.release_displays()

# --- I2C and sensor setup ---
i2c = busio.I2C(board.SCL, board.SDA)
bme280 = adafruit_bme280.Adafruit_BME280_I2C(i2c)

# Sea-level pressure for your location in hPa
# Standard atmosphere = 1013.25; adjust for your altitude
bme280.sea_level_pressure = 1013.25

# --- Display setup ---
display_bus = displayio.I2CDisplay(i2c, device_address=0x3C)
display = adafruit_displayio_ssd1306.SSD1306(display_bus, width=128, height=64)

# --- Build the display layout ---
splash = displayio.Group()
display.root_group = splash

# Background fill
bg_bitmap = displayio.Bitmap(128, 64, 1)
bg_palette = displayio.Palette(1)
bg_palette[0] = 0x000000
bg_sprite = displayio.TileGrid(bg_bitmap, pixel_shader=bg_palette, x=0, y=0)
splash.append(bg_sprite)

# Four text labels
title_label = label.Label(terminalio.FONT, text="  WEATHER STATION", color=0xFFFFFF, x=0, y=4)
temp_label  = label.Label(terminalio.FONT, text="Temp:  --.-  F",    color=0xFFFFFF, x=0, y=18)
hum_label   = label.Label(terminalio.FONT, text="Humid: --.-%",      color=0xFFFFFF, x=0, y=32)
pres_label  = label.Label(terminalio.FONT, text="Press: ---.- hPa",  color=0xFFFFFF, x=0, y=46)
feel_label  = label.Label(terminalio.FONT, text="Feels: --.-  F",    color=0xFFFFFF, x=0, y=60)

for lbl in (title_label, temp_label, hum_label, pres_label, feel_label):
    splash.append(lbl)


def heat_index(temp_f, humidity):
    """Rothfusz regression — accurate above 80 F and 40% RH."""
    if temp_f < 80 or humidity < 40:
        # Simple formula for mild conditions
        return 0.5 * (temp_f + 61.0 + ((temp_f - 68.0) * 1.2) + (humidity * 0.094))
    hi = (
        -42.379
        + 2.04901523 * temp_f
        + 10.14333127 * humidity
        - 0.22475541 * temp_f * humidity
        - 0.00683783 * temp_f ** 2
        - 0.05481717 * humidity ** 2
        + 0.00122874 * temp_f ** 2 * humidity
        + 0.00085282 * temp_f * humidity ** 2
        - 0.00000199 * temp_f ** 2 * humidity ** 2
    )
    return hi


print("Weather station running...")

while True:
    temp_c    = bme280.temperature
    humidity  = bme280.relative_humidity
    pressure  = bme280.pressure

    temp_f    = temp_c * 9 / 5 + 32
    feels_f   = heat_index(temp_f, humidity)

    temp_label.text  = f"Temp:  {temp_f:5.1f} F"
    hum_label.text   = f"Humid: {humidity:5.1f}%"
    pres_label.text  = f"Press: {pressure:6.1f} hPa"
    feel_label.text  = f"Feels: {feels_f:5.1f} F"

    print(f"T={temp_f:.1f}F  H={humidity:.1f}%  P={pressure:.1f}hPa  HI={feels_f:.1f}F")

    time.sleep(5)

How it works

Reading the BME280

The BME280 is a combined sensor that measures three environmental quantities over I2C in a single chip. After instantiating Adafruit_BME280_I2C, you access bme280.temperature (in Celsius), bme280.relative_humidity (percent), and bme280.pressure (hectopascals) as simple properties — the library handles all the register reads and compensation math internally. Setting bme280.sea_level_pressure lets the library also calculate altitude, though this project does not use that feature.

Driving the SSD1306 with displayio

adafruit_displayio_ssd1306 integrates with CircuitPython's displayio subsystem, which means you work with high-level Group, Label, and TileGrid objects rather than drawing pixels manually. You build a Group (a list of layers), attach Label objects at specific x/y positions, assign that group to display.root_group, and the display driver handles all rendering automatically. To update the screen you simply change a label's .text property — no redraw call needed.

The heat index calculation

The Rothfusz regression is the formula used by the US National Weather Service to calculate apparent temperature (what the air "feels like" accounting for humidity). At lower temperatures and humidity it simplifies to a linear approximation. The function in the code returns the same value in Fahrenheit that you would see on a weather app's "feels like" field. It is only meaningful above about 70 F — below that, humidity matters much less to perceived comfort.

Remix ideas

Remix idea

Log readings to the cloud. Add a WiFi-capable board (or swap to a Feather ESP32) and push temperature and humidity to Adafruit IO every minute. Then view charts and set up alerts from any browser. Start with Adafruit IO Basics.

Remix idea

Upgrade to a color TFT display. A 240×135 color TFT has room for large digits, a color-coded comfort scale, and a trend graph. See TFT Graphics builder for the display setup — the BME280 code stays identical.

Remix idea

Add air quality. Pair a PM2.5 particulate sensor or a SGP30 VOC sensor alongside the BME280 on the same I2C bus and add a fifth line to the display. The Air Quality Dashboard hacker page shows how to combine multiple environmental sensors.

Go deeper