Summer (mid May to late September) is hot, moderately dry, and sunny with a July and August having an average high of 33 °C (91 °F). The average depth of snow coverage is 2 to 4 cm (1 to 2 in), and the maximum is normally 6 to 13 cm (2 to 5 in), but some winters coverage can reach 70 cm (28 in) or more. The days are mild and relatively warm in mid spring.
Plovdiv sometimes experiences very hot days which are typical in the interior of the country. Autumn starts in late September; days are long and relatively warm in early autumn. The average January temperature is −0.4 °C (31 °F). The average relative humidity is 73% and is highest in December at 86% and lowest in August at 62%.
Although it was not the capital of the Province of Thrace, the city was the largest and most important centre in the province.
The ancient ruins tell a story of a vibrant, growing city with numerous public buildings, shrines, baths, theatres, a stadium, and the only developed ancient water supply system in Bulgaria. In 179 CE, a second wall was built to encompass Trimontium which had already extended out of the Three hills into the valley.
(39 sq mi), less than 0.1% of Bulgaria's total area.
It is the most densely populated city in Bulgaria, with 3,769 inhabitants per km². At the beginning of the 20th century, there were seven syenite hills, but one (Markovo tepe) was destroyed.
On average there are 33 days with mist during the year.
The history of Plovdiv spans more than eight millennia.Plovdiv is situated in a fertile region of south-central Bulgaria on the two banks of the Maritsa River.The city has historically developed on seven syenite hills, some of which are 250 metres (820 feet) high. It is an important economic, transport, cultural, and educational center.There is evidence of habitation in Plovdiv dating back to the 6th millennium BCE when the first Neolithic settlements were established; it is said to be one of the oldest cities in Europe.Because of these hills, Plovdiv is often referred to in Bulgaria as "The City of the Seven Hills".