A meteorological radiosonde, modified by the attachment of vertically oriented, pointed, metal rods, and associated insrumentation, was released beneath a thundercloud at Langmuir Laboratory, New Mexico. In addition to information on temperature and winds, the instrument provided an estimate of the vertical component of the cloud electric field by measurement of corona current induced in the rods. Charge volumes inferred from the sounding were (1) negative charge at 6.6 km msl (temperature -12 ¿C), where northwesterly winds apparently advected the charge toward the cloud's most intense precipitation echoes, (2) positive charge at 11.6 km msl (-50 ¿C) where the winds flowed northward into the cloud's anvil, (3) a 200-m-thick screening layer of negative charge at the cloud's upper surface, and (4) a small, concentrated region of charge near the cloud base. These charged regions were evident in volumes of low precipitation intensity (log Z≲1.5), which were well away from the storm's convective center.