September 2016, hot and dry
2016-10-21 (IPMA)
September was very hot and dry mostly due to the influence of an anticyclone located over the Azores region. The formation of low pressure systems of thermal origin in the interior of the Iberian Peninsula and the passage of frontal systems of low activity were the factors that regulated the weather in Portugal mainland.
The average mean air temperature was 21.51 °C, with an anomaly of +1.29 °C, regarding the normal 1971-2000, being that only in 14% of those years higher values of mean air temperature were reached.
The average value of maximum air temperature, 28.96 °C, was far superior to the normal value with +2.66 °C, matching the 3rd highest since 1931. The mean value of minimum temperature was close to normal.
On the 5th and 6th of September the mean values of air temperature were very high and records of maximum temperature were exceeded in a great part of the territory (73% of weather stations). With a mean temperature of 29.2 °C, 6th of September was the warmest day of the year in Portugal mainland. On this day the values of mean maximum air temperature, 38.6 °C and mean minimum air temperature 19.8 °C, were also the highest of the year.
A heat wave began on September 1st and occurred in most parts of the North and Center regions and inner Alentejo.
Regarding rainfall, the month was generally dry. The total of precipitation was of 58% of the normal value. However, strong rain occurred in the Northwest region, on 13th and 24th of September and in some places the daily value of rainfall was above 20 mm.
