Noonday is a city in Smith County, Texas, United States. The population was 612 at the 2020 census. It is part of the Tyler, Texas Metropolitan Statistical Area. Noonday is perhaps best known for the "Noonday Onion," reputed to be one of the sweetest onions available. An onion must be grown within a ten-mile radius of Noonday in order to be considered a "Noonday Onion". The "Noonday Onion Festival" is held each year in May.