Evidence that elevated temperatures can lead to increased mortality and morbidity is well documented, with population vulnerability being location specific. The elderly are particular vulnerable to extreme heat stress. Being part of the Iberian Peninsula, Portugal has a mild Mediterranean climate. Climate change projections indicate that the number of days with extreme heat in Portugal will increase with urban areas being more sensitive. If future populations become more urbanized and the number of elderly continues to increase, the issue of heat-related mortality will likely become more severe.

During the 2003 heatwave in Europe, Portugal was one of the few countries that already had an early warning system in place: but only for Lisbon, the capital city. Following the 2003 heatwave, the Portuguese Heatwave Contingency Plan was established and has been in operation every year from May to September. This is a national plan covering the whole continental Portugal. The aim of the current Portuguese Heatwave Contingency Plan is to prevent the adverse health effects of heat stress on the population during periods of elevated temperatures. Daily alerts are key factors to the successful implementation of this plan; they indicate what protection measures must be carried out to protect the population during periods of elevated temperatures.