The market-implied certainty on a 76-77°F high for New York City on May 16 stems from the official maximum temperature recorded at LaGuardia Airport (KLGA), the designated station for resolution. National Weather Service observations and nearby mesonet data aligned precisely with this range after accounting for urban heat island effects and afternoon mixing, while ensemble guidance from the GFS and ECMWF had converged on peak readings in that narrow window the prior evening. Historical climatology for mid-May shows an average high near 72°F at the site, making the observed value slightly above normal but well within expected variability for a transitional spring pattern. Only an undetected sensor error or post-event data revision at the primary station could shift the outcome outside this bin.