The highest peaks of Costa Rica (9°15′– 9°36′N) were glaciated during the late Quaternary, attesting to a significantly cooler climate in Central America than today. During the last local glacial maximum (LLGM), an ice cap ∼35 km2 in extent covered the highest peaks of the Cordillera de Talamanca around Cerro Chirripó, and around Cerros de la Muerte and Kamuk, ∼5 and 2 km2 of ice existed, respectively. In Chirripó National Park, three moraine groups define three glacial stages. The Talamanca Stage extends to 3040 m and represents the last local glacial maximum. Chirripó Stage moraines reach elevations of 3300 m, and Talari Stage moraines formed at ∼3300 and 3420 m. Former equilibrium- line altitudes (ELAs) were ∼3500 m, ∼3600 m, and ∼3620 m, respectively. Cirque-floor elevations of 3260 m at Cerro Kamuk suggest a lower (pre-?)LLGM ELA. Radiosonde data from San José place the modern 0 °C isotherm at ∼5000 m, which suggests a late Quaternary ELA depression of ∼1500 m, which is consistent with a temperature reduction at Chirripó of 8–9 °C during the LLGM. Some of this cooling may be attributable to a steeper lapse rate associated with a drier atmosphere, possibly due to a more restricted position of the Intertropical Convergence Zone, decreased yearly convection, or more frequent incursion of polar air masses.