Rain detection system and method for controlling the same

A rain detection system generates an operation signal for operating a wiper system on a window (7) based on a detected window condition. The rain detection system includes a detection means (41) for intermittently detecting an amount of liquid on the window (7), a calculation means (44) for calculating an increase rate of the amount of the liquid detected in a detection operation by the detection means (41) and a determination means (45) for determining the window condition based on the increase rate calculated by the calculation means (44). The determination means (45) distinguishes difference between condensation on the window (7) and rain based on the detected liquid on the window (7).