Fall frost events are common in the corn belt of the United States. Frost events can cause damage to seed tissue by initiating ice formation. Genotype and moisture content can affect seed freezing characteristics of maize. Previous studies on maize seed freezing have used constant temperatures or steady cooling rates. The goal of this study was to determine freezing characteristics of two hybrids harvested at three moisture contents and exposed to a frost cycle mimicking a natural frost event. Two hybrids were produced from B73 and Mo17 female lines pollinated with IRF311. During seed maturation, ears were harvested at 500-550, 400-450, and 300-350 g kg-1 with the husks and shanks intact. The frost cycle mimicked a severe fall killing frost in the Midwest. The cycle duration was 24 h, beginning and ending at 10°C. It included air temperature below 0°C for 8 h and -5°C for 2 h, which would be considered a severe killing frost. Hypodermic needle probes containing 30 gauge copper-constantan thermocouples were inserted into the embryo without disturbing the husk or surrounding seeds. Unsheathed 36 gauge copper-constantan thermocouples were placed on the husk surface, underneath the first layer of husk, and inserted underneath all husk layers by insertion through the silks. Data was recorded from each thermocouple every second. Ice formation occurred at all moisture contents as shown by exothermic peaks. Genotypes and moisture contents were compared using the supercooling point (SCPT) and supercooling amount (SCAMT). SCPT decreased as moisture content decreased. SCAMT was greater for Mo17xIRF311 than B73xIRF311.