The climate of Prague is mild. The average yearly air temperature in Prague reaches 9°C. The highest daily temperatures could reach more then 30°C
during summer time. During winter the lowest temperatures could be lesser then -20°C. The yearly rainfall is about 680 mm.
Like in other European cities, traffic is again identified as the main source of poor air quality leading to problems for PM10, nitrogen dioxide,
carbon monoxide, benzene, benzo(a)pyren and ozone. Prague belongs between the most polluted areas in the Czech Republic.
Emission production of the most of pollutants were decreased in last years however the air quality is still the biggest problem of Prague's environment.
The main source of air pollution comes from traffic, which can by hardly regulated. The number of cars per 1000 inhabitants in Prague grew twice time
from 1990 to 2000.
Because of the bad ventilation conditions of Prague relief and big traffic emissions are exceeded the limits for health protection of the suspended
particulate matter, nitrogen dioxide, carbon monoxide, ground-level ozone and benzene. The limits are exceeded in 28% of the city area.
The adverse environmental effects of stationary energy sources in Prague have been significantly reduced over the last decade, pollutants emissions
dropped from three to ten times. The persistent high air pollution in Prague has been caused, to the greatest extent, by traffic, which has been
producing approx. 80–90 % of total emissions of critical pollutants (NO2, benzene, CO).
The relatively high percentage of small sources in the CO emissions is mostly due to oversized power output of boilers installed in family houses
and their mode of operation when only a fraction of the installed output is utilised. The stationary energy sources have important effects on solid
emissions – 52 %. Significant problem is the air pollution by particles due the extensive re-suspension of road dust and secondary aerosols production
from the gaseous pollutants. The sulphur oxides emissions from stationary energy sources account for 95 % of the total amount thereof nevertheless
sulphur emissions do not pose a critical issue concerning air pollution.
Generally, for air quality management the most troublesome issue is the exceeding of limit values for nitrogen oxides – namely in the surroundings of
frequented traffic routes and in the centre. Of the total nitrogen oxides emissions on the Prague territory 82 % are traffic related and 4 % go to low-level
emission from small area sources. Local area sources, including the local combustion of natural gas and solid fuel contribute to the nitrogen oxides
concentrations within the range form 5 to 50 % in the downtown with limit-exceeding air pollution.