Strong cooling events off the western barrier reef of New Caledonia have been recently observed and attributed to wind-driven coastal upwelling. A simple one-dimensional model based on a heat budget in the mixed laxer is developed and calibrated to explain the daily variations of sea surface temperature (SST) observed at a coastal station off southwestern New Caledonia from 1992 to 2005. This model takes into account the daily wind-forced vertical advection and air-sea heat fluxes, as well as seasonal variations of the subsurface temperature stratification. It can explain a large part of the daily SST variations and helps to quantify the relative contribution of the main vertical processes involved in these variations. The model shows that upwelling is the dominant process at daily timescale, and its SST signature is strongly modulated by the seasonal variations of the subsurface stratification. The surface heat fluxes have a smaller influence than upwelling on daily SST variations. Coastal chlorophyll a concentration increases during upwelling events.