The yellow weather warning for these three districts will be in effect between 12pm and 6pm today.
The IPMA forecasts periods of very cloudy skies and showers on the continent today, occasionally heavy in the South, which may be accompanied by thunderstorms during the afternoon.
The forecast also indicates light to moderate winds and a slight rise in temperature, mainly in the North and Central regions.
Minimum temperatures will range between 5 degrees Celsius (in Guarda) and 14 (in Faro) and maximum temperatures between 14 (in Guarda) and 22 (in Faro, Setúbal and Santarém).