Relationship of outgoing long-wave radiation (OLR) with convective available potential energy (CAPE) and temperature at the 100-hPa pressure level is examined using daily radiosonde data for a period 1980–2006 over Delhi (28.3˚N, 77.1˚E) and Kolkata (22.3˚N, 88.2˚E), and during 1989–2005 over Cochin (10˚N, 77˚E) and Trivandrum (8.5˚N, 77.0˚E), India. Correlation coefficient (Rxy) between monthly OLR and CAPE shows a significant (∼−0.45) anti-correlation at Delhi and Kolkata suggesting low OLR associated with high convective activity during summer (seasonal variation).