A probe consisting of a stainless steel rod covered by a Teflon sheath set inside a cylindrical rainwater collector. The water surrounding the probe forms the outer plate of a coaxial-type capacitor while the metal rod forms the inner plate. The Teflon sheath serves as the dielectric. As the water height in the collector rises, the surface area of the capacitor increases, increasing the total capacitance. The total capacitance is measured and converted to an analog voltage directly proportional to the height of the water in the collector.