The Portuguese Institute of the Sea and Atmosphere (IPMA) placed at very high risk around 80 municipalities in the districts of Bragança, Vila Real, Braga, Porto, Viseu, Guarda, Coimbra, Castelo Branco, Leiria, Santarém, Portalegre, Beja and Faro.
The IPMA also placed at high risk almost the entire Alentejo region and over 40 other municipalities in the districts of Viana do Castelo, Vila Real, Porto, Braga, Aveiro, Coimbra, Leiria, Santarém and Lisbon.
The remaining territory presents a moderate and low risk, depending upon the region.
On Tuesday the IPMA warned of a rise in the risk of fire and an increase in temperatures until the weekend, when the thermometers are expected to breach the 40 degree mark in some regions of the country.
The fire risk determined by IPMA has five levels, ranging from reduced to maximum.
Calculations are obtained from air temperature, relative humidity, wind speed and amount of precipitation in the last 24 hours.
The critical period of fires lasts until the end of September and, until then, it is prohibited to make extensive fires or burn without authorization, to use grills throughout the countryside, and to smoke or make any kind of fire in forest areas.
According to the IPMA, it is expected that by the weekend the highest temperatures will be registered in the interior north and centre, as well as in the interior of the Alentejo and in some parts of the Algarve. For the north and central coast, a rise in temperature is expected from Friday.
And because of the increase in temperatures, from 12:00 today until 18:00 on Friday, there are seven districts that will be under a yellow weather warning due to the heat: Vila Real, Bragança, Guarda, Castelo Branco, Portalegre, Évora and Beja.
For today, the IPMA forecasts a slight rise in temperature in mainland Portugal, especially in the interior, with generally clear skies. The wind will sometimes be strong in the western coastal strip and in the highlands.
The maximum temperatures will vary between 24º (Aveiro and Porto) and 38º (Évora and Castelo Branco) and the minimum between 14º (Bragança, Viana do Castelo and Porto) and 21º (Faro and Portalegre)