High atmospheric temperature and humidity can cause discomfort and even death among people in high-risk groups. Forecasting such meteorological situations can be a useful tool for public health managers. The predictability of discomfort is analysed using a time series of the relative strain index in Buenos Aires. Other authors have found that index values exceeding the thresholds of both nocturnal and diurnal comfort can increase mortality. This study finds that such situations are associated with index values over 0.20 at 14:00 h. local time (RSI14>0.20). Consequently, the meteorological conditions associated with RSI14≥0.20 are studied. The anomalies of the geopotential monthly mean fields show the passage of a low-pressure system south of 45°S. This system is related to a trough, possibly of frontal character, moving across the province of Buenos Aires, and a simultaneous intensification of the north-western low in Argentina. The synoptic situation is associated with a general northerly flow that brings heat and moisture from the tropics. On 81% of days with RSI14=0.20, winds with a northerly component were recorded. This increases to 84.4% when at least one day with northerly wind is previously observed. The synoptic characteristics are examined using a combination of circulation indices: meridional (R), zonal (Z) and curvature (C). The daily sequence of the weighted averages of the anomalies obtained are ΔR<0, ΔZ>0 and ΔC>0. Some 67% of the days when RSI14=0.20 correspond to this daily index pattern estimated at locations near Buenos Aires.