Diurnal sea breeze events can have a strong but uncertain impact on coastal air quality. In this study, using 10 years of observations we show that sea breeze occurs mostly when the sea is cool, wind speeds low, and solar irradiance strong. Surface of gas and particulate pollutants are all higher during sea breeze events than on other days, increasing the rate of air quality regulation exceedance. This may be of concern for beach goers and for people who spend more time outdoors.