To guarantee the quality in the coffee production, not only the harvesting process is important, but also the subsequent processes are critical for maintaining a high quality coffee to achieve export quality of the coffee grains. One of those processes is the drying, which should lower the coffee moisture to a 10%-12%. However, there are not affordable technologies for little farmers able to detect when the moisture level is in the optimal range. Therefore, we propose a Wireless Sensor Network (WSN) using LoRaWAN for monitoring and studying the environmental variables that affect the drying process. We collect data about the humidity, temperature, and luminosity of the surroundings of the drying boxes where the coffee is placed, and analyze it to understand the relation of each variable with the coffee moisture level. Finally, we generate a model with regression equations to predict when the drying process is at the finishing state.