When may rain repellent be applied to a windshield?

Rain repellent should be applied to a windshield prior to the onset of rain to maximize its effectiveness. The purpose of rain repellent is to enhance visibility during wet conditions by causing water to bead up and roll off the windshield, rather than gathering and obstructing the driver's view.

If applied after rain begins, it may not provide optimal results because the rain could wash away some of the repellent, or the existing water on the windshield could interfere with its bonding to the glass. Additionally, applying it to a wet windshield can lead to uneven coverage and poor performance.

Using rain repellent on a dry windshield helps ensure that it adheres properly and forms an effective barrier against rainwater. Waiting until precipitation has started or is ongoing to apply the product does not take advantage of the ideal conditions for application, thus reducing its effectiveness during the actual rain event. Therefore, the strategic timing of application prior to entering rainy conditions is essential for this product to function as intended.