Tatiana-2 datacan be obtained from S.B. Jiang atthe National Central University(t330008@cc.ncu.edu.tw).FORMOSAT-3/COSMIC data areavailable at Taiwan Analysis Centerfor COSMIC (http://tacc.cwb.gov.tw/)and/or COSMIC Data Analysis andArchival Center (http://cdaac-www.cosmic.ucar.edu/cdaac/), whileDEMETER data can be retrieved fromhttp://demeter.cnrs-orleans.fr/. ; International audience ; It has been well known that the ionospheric electron density N e is greater in the summer nighttime than daytime around the Weddell Sea region, which is named Weddell Sea Anomaly (WSA). This paper for the first time reports unusual increases (decreases) of the daytime (nighttime) electron temperature T e at about 830 km altitude over the WSA latitudes probed by Tatiana-2 during December 2009 to January 2010. Concurrent measurements at 660–830 km altitude observed by Tatiana-2, Detection of ElectroMagnetic Emissions Transmitted from Earthquake Regions (DEMETER), and Formosa Satellite 3/Constellation Observing System for Meteorology, Ionosphere and Climate (F3/C) reveal the anticorrelation between T e and N e along the WSA latitudes in the daytime and nighttime. Based on F3/C N e along the WSA latitudes observed at various local times, the associated T e values are computed. The Tatiana-2 and DEMETER observations as well as the computed results show that T e yield the maximum values over the WSA region during daytime and over the Indian and Atlantic Ocean area during nighttime. The maxima or minima in F3/C N e and the computed T e reveal eastward phase shifts.