The Adafruit HTS221 is an affordable I²C/SPI temperature and humidity sensor breakout board from ST. It measures relative humidity from 0–100% RH with 3.5% accuracy (in the 20–80% range) and temperature from -40 to 120°C with ±0.5°C accuracy (between 15 and 40°C). An excellent choice for everyday environmental monitoring applications.

The breakout includes STEMMA QT / Qwiic connectors for solderless I²C hookup, along with standard header pins for breadboard use. On-board level shifting and a voltage regulator make it compatible with both 3.3V and 5V microcontrollers.

Key Features

• 0–100% Relative Humidity Range – 0.004% sensitivity, 3.5% accuracy (20–80% RH)
• -40 to 120°C Temperature Range – 0.016°C resolution, ±0.5°C accuracy (15–40°C)
• I²C and 3-Wire SPI Interfaces – Flexible connectivity options
• STEMMA QT / Qwiic Connectors – Solderless I²C connection, compatible with SparkFun Qwiic
• 3.3V and 5V Compatible – On-board level shifting and voltage regulation
• Arduino and CircuitPython Libraries – Ready-to-use driver support with example code

Ideal For

• Indoor climate and environmental monitoring
• Greenhouse and mushroom farming humidity tracking
• Weather station projects
• Beginner-friendly sensor projects with solderless STEMMA QT connection

Package Contents

• 1× Adafruit HTS221 Breakout Board – Assembled and tested with STEMMA QT connectors
• 1× Header strip (unsoldered)

Resources

• Adafruit HTS221 Learn Guide
• What is STEMMA QT?