A desert climate
Almost the entire Arabian Peninsula is subject to a desert climate. This means that temperatures are very high during the day, with a large day/night temperature range. On average, temperatures in Riyadh exceed 40°C from June to September. In winter, from November to March, temperatures average below 30°C, the coldest month being January, with an average daytime temperature of 19°C and 11°C at night. The interseasons are very short. In April and May, temperatures gradually rise to stabilize around 35°C, as well as in October, when the phenomenon is reversed and temperatures drop more sharply. The thermal amplitude day/night varies between 8 and 20 °C, the lowest amplitudes being recorded in winter.
The desert climate is characterized by a dry climate, but the coastal areas along the Red Sea and the Persian Gulf are very humid, due to evaporation from the sea. The cities of Jeddah, Mecca, Medina or Dammam are stiflingly hot. Mecca is the hottest city in the country, but the heat record is held by Jeddah, with 52 ° C recorded on June 22, 2010. Jeddah is generally a few degrees warmer than Riyadh in all seasons and has a smaller day/night temperature range.
There can be large temperature differences within the country at any given time. This is due to the size of the country - more than 2,000 kilometers separate the north from the south - but especially due to significant differences in elevation. For example, in Tabouk, a city in the north built at an altitude of 750 meters, it is advisable to cover yourself with a down jacket, hat, scarf and gloves in winter, while a small sweater is sufficient in Jeddah.
The climatic exception of the Southwest
The province of Asir, crossed by a mountain range, has a semi-arid climate, with limited rainfall although more important than in the rest of the country. Located in the southwest of the country, between the provinces of Mecca in the north and Jazan in the south, it is in this region that the highest peak in Saudi Arabia at 3,133 meters, the jabal Sawda. The thermal amplitude is one of the most important in the world. If the temperatures flirt with 30 ° C during the day and in all seasons, it is not uncommon to wake up with frost on the windows and fog so thick that visibility is close to zero. It can snow in winter. For these reasons, the Asir region is the greenest in Saudi Arabia, but it also requires appropriate clothing.
Waiting for the rain
Saudi Arabia has very limited rainfall. In Riyadh, the capital located in the center of the country, the average annual rainfall is 110 mm. Winters have low rainfall, with a peak in March and April. Over this period, the average recorded is 270 mm. The province of Asir, the most rainy in the country, records an annual average of 500 mm, with also, a period of greater rainfall in March and April. It does not rain in the country during the 4 summer months, which run from June to September. Saudi Arabia's annual rainfall is below the potential evapotranspiration threshold. Evapotranspiration is a biophysical phenomenon that sees the evaporation of water contained in plants and soils to the atmosphere. Therefore, the scarce rainfall that does fall in Saudi Arabia is immediately absorbed by soils and plants and does not return to the atmosphere to generate new rainfall, unlike what happens in tropical countries.
