Microbarographs situated 66 to 1000 km south-southeast from Helgoland recorded disturbances initiated by the five-thousand-ton TNT explosion on that island 18 April 1947. Special balloons at four meteorological stations obtained weather data to 29.5 km altitude at blast time. Wind velocities are considered negligible up to balloon summits. Assuming negligible winds at higher altitudes, interval velocities of abnormal microbarometric signals permit calculations of upper-atmosphere temperatures. Temperature rises steeply from 221K at 32 km to 285K at 42.5 km, then more slowly to 294K at 55 km. Very long period waves recorded beyond 400 km are believed to have returned from the second high-temperature region of the upper atmosphere. Arrival times are best matched by assuming a cold layer between 55 and 86 km, with lowest temperature 170K extending from 64 to 79 km. A steep rise to 296K at 86 km precedes a smaller gradient to 399K at 172 km. Not much confidence is held in results above 100 km.