Chances are, if your windshield wipers automatically turn on when it starts to rain, your car has rain sensors. Most cars have the controls to turn the rain sensor auto wipe system on or off on the steering wheel column. When I am driving around and the rain is barely sprinkling, yet sprinkling enough to bug me, I end up turning the rain sensors on and off.

From wikipedia:

A rain sensor or rain switch is a switching device activated by rainfall. 

In 1958, the Cadillac Motor Car Division of General Motors experimented with a water-sensitive switch that triggered various electric motors to close the convertible top and raise the open windows of a specially-built Eldorado Biarritz model, in case of rain. The first such device appears to have been used for that same purpose in a concept vehicle designated Le Sabre and built around 1950–51. For Model Year 1996, Cadillac once again equipped cars with an automatic rain sensor; this time to automatically trigger the windshield wipers and adjust their speed to conditions as necessary.^{[citation needed]}

Heh. I once picked up a bf’s uncle’s Eldorado Biarritz and never knew the windshield wipers went on automatically.

Video of Toyota rain sensor system

And be sure to replace your wiper blades every 6 months. Most people replace their blades when they start “chattering” due to road grime and grease build up, but because we have so much rain in Hawaii, it’s good practice to keep new blades on your vehicle.

Ace Auto Glass