The ever-increasing need for precision, accuracy, reliability, and real-time continuous environmental measurement for agriculture, warehousing, and laboratory use has revealed shortfalls in conventional hygrometers, namely, measurement accuracy, lack of real-time remote monitoring, and insufficient data logging functionality. The main objective of this study is to create and calibrate an Internet of Things-based hygrometer system with real-time accuracy for temperature and relative humidity measurement. The proposed system comprises a DHT22 (AM2302) digital temperature and humidity sensor, an ESP32 Wi-Fi microcontroller, a local visual display using a liquid crystal display module, and a cloud interface for remote graphical and storage functionality. The system utilized C++ programming for sensing, processing, and transmitting data wirelessly. Additionally, calibration of the system was performed using three standard digital hygrometers for improved accuracy and reliability. Experimental findings showed that before calibration, Sensors A and B had a temperature difference and a humidity difference of +0.7 °C and a 1% relative humidity (RH) delay, respectively. After calibration, the sensor showed a system accuracy of ±0.2 °C and ±2–5% RH for temperature and humidity measurement, in accordance with manufacturer specifications. The system demonstrated a real-time response with update intervals of 15 seconds while maintaining stable performance for a temperature range of −40 °C to 80 °C and humidity conditions from 0% to 100% RH. Through the integration of Internet of Things connectivity with sensor calibration, the developed system enables a cost-effective, accurate, and remotely accessible solution for environmental monitoring, supporting enhanced decision-making in precision agriculture, lab monitoring, and industrial climate control.