As a Siberian city, Irkutsk experiences a subarctic climate, characterized by extreme variation of temperatures between seasons. Temperatures can be very warm in the summer, and brutally cold in the winter. However, Lake Bajkal takes its effect, such that temperatures in Irkutsk is not as extreme, as elsewhere in Siberia. The warmest month of the year in Irkutsk is July, when the mean temperature is , the highest temperature recorded being 37 C. The coldest month of the year is January, when the mean temperature is only . Precipitation also varies widely throughout the year, with the wettest month also being July, when precipitation averages 119 mm (4.70 in). The driest month is February, when precipitation averages only 7.6 mm (.30 in), mainly due to the fact that almost all precipitation during the Siberian winter falls as fluffy, low moisture content snow.
In the early 19th century, many Russian artists, officers, and nobles were sent into exile to Siberia for their part in the Decembrist revolt against Tsar Nicholas I. Irkutsk became the major center of intellectual and social life for these exiles, and much of the city's cultural heritage comes from them; many of their wooden houses, adorned with ornate, hand-carved decorations, survive today in stark contrast with the standard Soviet apartment blocks that surround them.
By the end of the 19th century there was one exiled man per two locals. Different people from the members of the Decemberists' uprising to Bolsheviks have been staying in Irkutsk for a long time. These people have greatly influenced the culture and the development of the city and it has finally became a prosperous cultural and educational center for Eastern Siberia.
1879, on July 4 and 6, the palace of the (then) Governor General, the principal administrative and municipal offices and many of the other public buildings were destroyed by fire; and the government archives, the library, and the museum of the Siberian section of the Russian Geographical Society were utterly ruined. Three quarters of the city were destroyed, including approximately four thousand houses. However, the city quickly rebounded, with electricity arriving in 1896, the first theater being built in 1897, and a major train station in 1898. The first train arrived in Irkutsk on August 16 of that year. By 1900, the city had earned the nickname "The Paris of Siberia."
During the civil war that broke out after the Bolshevik Revolution, Irkutsk became the site of many furious, bloody clashes between the "Whites" and the "Reds". In 1920, Kolchak, the once-feared commander of the largest contingent of anti-Bolshevik forces, was executed there, effectively destroying the anti-Bolshevik resistance.
During the Communist years, the industrialization of Irkutsk, and Siberia in general, was heavily encouraged. The large Irkutsk Reservoir was built on the Angara between 1950 and 1959 in order to facilitate industrial development.
The Epiphany Cathedral (illustrated, to the right), the governor's palace, a school of medicine, a museum, a military hospital, and the crown factories are among the public institutions and buildings. The Alexander Kolchak monument, designed by Vyacheslav Klykov, was unveiled in 2004. On July 27, 2004, the Irkutsk Synagogue (1881) was gutted by a conflagration.
The emblem of Irkutsk features an old symbol of Dauria: a Siberian tiger with a sable in his mouth. When the emblem was devised in 1690, the animal was described as a tiger ("babr", a bookish word of Persian derivation) with a sable in his mouth. This image had been used by the Yakutsk customs office from about 1642. It has its origin in a seal of the Siberia Khanate representing a sable and showcasing the fact that Siberia (or rather Yugra) was the main source of sable fur throughout the Middle Ages. (Actually, the English word "sable" is derived from the Russian "sobol").
By the mid-19th century, the word "babr" had fallen out of common usage, but it was still recorded in the Armorial of the Russian Empire. Furthermore, the tigers became extinct in this part of Siberia. In the 1870s, a high-placed French heraldist with a limited command of Russian assumed that "babr" was a misspelling of "bobr", the Russian word for "beaver", and changed the wording accordingly. This modification engendered a long dispute between the local authorities, who were so confused by the revised description that they started to depict the "babr" as a fabulous animal, half-tiger and half-beaver.
The Soviets abolished the image altogether, but it was restored following the dissolution of the Soviet Union.
Important roads and railways like the Trans-Siberian Railway connect Irkutsk to other regions in Russia and Mongolia. Also, the city is served by the Irkutsk International Airport and the smaller Irkutsk Northwest Airport.
The Federal road to Vladivostok passes through a suburb of Irkutsk.