Hotter still is the core. In the sun this is thought to be 10 - 20 million degrees. These temperatures are due to the pressure caused by gravity trying to compress the star. It has to be this temperature for fusion of hydrogen to take place. Once fusion starts in a young star this adds to the temperature to ensure that fusion continues.
Weather in Lisbon in September. The average maximum daytime temperature in Lisbon in September is a warm 27Â°C (81Â°F) with low heat & humidity. There are usually 9 hours of bright sunshine each day, which represents 68% of the 12 hours of daylight. The average sea temperature in and around Lisbon in September is 19Â°C (66Â°F). Expect 26mm (1.0 inches) of rainfall across the whole of September with 6 days with some rain falling. Maximum UV levels will be high (6 UV index) at midday when the skies are clear.
Lisbon: Annual Weather Averages. July is the hottest month in Lisbon with an average temperature of 24Â°C (74Â°F) and the coldest is January at 11Â°C (52Â°F) with the most daily sunshine hours at 9 in May. The wettest month is November with an average of 127.6mm of rain. The best month to swim in the sea is in September when the average sea temperature is 20 Â°C (68 Â°F). Average Temperature: Lisbon