METEOROLOGICAL CONDITIONS

Last update
20.09.2012

Key question

What was the development of meteorological conditions in the Czech Republic´s territory in 2011?

Key message

	In the territory of the Czech Republic, the year 2011 showed above-average temperatures; from the perspective of annual rainfall it was average but much drier than the previous year. The average annual air temperature (8.5 °C) was by 1 °C higher than the long-term mean in 1961–1990. The annual rainfall amounted to 627 mm, which represents 93% of the long-term mean in 1961–1990. Rainfall distribution during the year was uneven; there were both very dry and very wet months.
	The year 2011 was characterized by very warm early spring and by rainfall-rich July. The peak of the summer was at the end of August and November was extremely dry. The year 2011 was unique for its almost zero rainfall in November, even as regards the whole history of measurement and observation in the Czech Republic´s territory.
	During the months of January through March, and also in November, there were longer periods with adverse dispersion conditions. In the region of Ostrava and Karviná, the regulation signal was announced for 37 days and the warning signal for 24 days in total.

Overall assessment	Change since 1990	Change since 2000	Last year-to-year change
	N/A	N/A	N/A

Weather conditions affect the environmental burdens as well as the state of the environment. Long-term development of temperature and precipitation conditions is used to detect climate change and to evaluate it.

Temperature and precipitation conditions in a given year have an impact on the national economy, especially as regards the sectors of energy, agriculture, water management and forestry, and thus on the level of the environmental burdens caused by these sectors. The weather conditions directly affect the state of the environment, too. They can influence the dispersion conditions for pollutants in the atmosphere and - in turn -air quality, especially in the winter. In the summer period, high temperatures combined with intense solar radiation cause the formation of tropospheric ozone. High temperatures also increase the evaporation rate and, when combined with rainfall deficiency, they decrease soil humidity, affect drainage conditions, increase the eutrophication rate of still waters and, last but not least, may also result in fires. Deepening extremity of the climate, associated with more frequent occurrence of hazardous hydrometeorological phenomena, such as floods, long-term drought or very strong wind, can cause extensive damage to the national economy.

Chart 2: Monthly average air temperature (for the last available year, see data) (areal averages* compared to the 1961–1990 long-term mean), the Czech Republic [°C]
Source: The Czech Hydrometeorological Institute

Chart 3: Monthly precipitation totals (for the last available year, see data) (areal averages* compared to the 1961–1990 long-term mean), the Czech Republic [mm]
Source: The Czech Hydrometeorological Institute

Indicator assessment – text part

The year 2011 was very warm in the Czech Republic; the annual average temperature (8.5 °C) was by 1 °C higher than the 1961–1990 long-term mean. Due to this temperature, the year 2011 was the seventh hottest year since 1961, and, at the same time, the fifth hottest year since the beginning of 21st century (the hottest years at all were the years 2000 and 2007). In comparison with the previous year 2010, which was the coolest year since 2000, the year 2011 was by 1.3 °C warmer. The average monthly air temperatures were varying around the mean values of the period 1961–1990; the months of April, August and December were very warm compared to the mean.

The weather was changeable at the beginning of the year, while frost periods were alternating with times of temperatures being high above the long-term average. The average January temperature (-1.2 °C) was by 1.6 °C higher than the 1961–1990 mean and the month was normal in terms of temperature. The weather was cooler in February; the average temperature reached the value of – 2 °C, which is by 0.9 °C less than the 1961–1990 mean. The lowest minimum temperature of the air -28 °C was recorded on 24th February at the meteorological station in Kořenov - Jizerka. Frosty weather at the end of January, in the course of February and in early March was connected with worsened dispersion conditions for air pollutants. In the Moravian-Silesian region, the regulation signal was in force for 37 days and the warning signal for 24 days of the whole year (including the November episode). The total duration of the regulation and warning signals in 2011 was slightly higher compared with 2010, not only in the Moravian-Silesian region but also in the other regions of the Czech Republic.

There was very warm weather in April; the average April temperature (10.5 °C) was by 3.2 °C higher than the 1961–1990 mean. As early as at the beginning of the month, the first summer day (i.e. a day with the maximum air temperature being 25 °C and more) was recorded in Prague; the maximum air temperature at the meteorological station in Prague - Karlov reached 25.6 °C on 3rd April. The maximum air temperature over 25 °C was recorded at a number of stations in the third decade of the month, too. Rapid cooling with minimum temperatures below the freezing point in the first decade of May caused extensive damage, not only for wine growers but also for orchardists and growers of other crops. On 4th May, the minimum air temperature in mountain valleys fell below -10 °C but it remained below the freezing point also in lowlands, e.g. in Pardubice it fell to -2.8 °C, in Semčice to -2.8 °C, in Kroměříž to – 0.9 °C.

The warmest summer month was August, with the average monthly temperature being 18 °C, which is 1.6 °C more than the 1961–1990 mean; the month was therefore very warm. A heat wave with the maximum daytime temperatures above 30 °C hit the Czech Republic in the third decade of the month and it continued till early September. The highest maximum air temperatures in Bohemia and Moravia were recorded on the same day - on 26th August the maximum air temperature in Chotusice got up to 36.7 °C, in Strážnice to 36.1 °C.

Temperatures in the months of October and November were more or less normal; December was a very warm, with average monthly air temperature being 1.9 °C which is by 2.9 °C more than the 1961–1990 mean. The average daily temperature in the Czech Republic was oscillating above the values of the long-term monthly mean for nearly the whole month; it was lower for only 3 days. A warm end of the year has also been reflected in the low number of days with extreme temperatures. In 2011, there have been 28 icy days and 117 frosty days, which is less than in 2010.

Occurrence of tropical days in the Czech Republic´s territory in 2011 was lower in comparison with 2010 and it varied around the mean (5 days per year). Most tropical days were recorded at the end of August and at the beginning of September. By contrast, occurrence of summer days was slightly higher compared with the previous year (42.1 days on average for the Czech Republic), which is an above-average value in comparison with the 1961–1990 mean, as well as in all the years since 2000. The above-described occurrence of characteristic days indicates less extreme but generally warmer course of the year 2011 compared to 2010.

The annual rainfall (precipitation total) in the territory of the Czech Republic amounted to 627 mm, which represents 93% of the 1961–1990 long-term mean, and the year as a whole was evaluated as normal in terms of precipitation. Distribution of rainfall throughout the year, however, has been uneven; there have been both very dry and very wet months. Low rainfalls with values much below the monthly mean were recorded in February and November, and conversely, July was very moist.

The January rainfall (41 mm) represented 97% of the 1961–1990 long-term mean, the month was therefore normal in terms of precipitation. However, as a result of warming and abundant precipitation in the second decade of January, there were elevated river levels and different levels of flood activity were achieved in the Czech Republic. The highest flow rates were recorded in South Bohemia in the lower course of the River Lužnice and the River Skalice, in the West of the Czech Republic´s territory they were in the tributaries of the River Berounka.

February was very dry; the monthly rainfall of 10 mm is only 27% of the 1961–1990 mean. As a result of dry weather, there was snow cover at the lower and middle altitudes only at the beginning of the month (before the snow melted during warm-up in the half of the first decade); there was no snow at all in the lowest altitudes in South Moravia in February. The biggest amount of snow has fallen in the Giant Mountains while the highest maximum seasonal height of the total snow cover reached 120 cm in Labská bouda, which is by almost 50 cm less than the long-term mean for this meteorological station.

The rainfall in July has been high above the mean; the area rainfall for the whole of the Czech Republic, which amounted to 145 mm, was 184% of the mean value. Most of the precipitation fell in North Bohemia; the highest monthly rainfalls were recorded in the stations located in the region of Liberec, namely Josefův Důl (466.7 mm), Bedřichov (461.6 mm) and Mníšek-Fojtka (422 mm). Due to the fact that in this area, damage of the 2010 floods has not been removed entirely, it is not possible to evaluate the state of the flow rates in the individual watercourses accurately. Thanks to lower flood intensity in comparison with the previous year, the property damage was not high.

In terms of precipitation, the months of September and October were oscillating around mean values. Extremely dry weather was recorded in November, not only in the territory of the Czech Republic but also in the whole of Central Europe. The monthly rainfall of 1 mm, which is only 2% of the long-term mean, puts this month among the driest months in the history of observations in the Czech Republic. Almost 80% of all stations which measure precipitation in the Czech Republic´s territory have recorded zero rainfall or rainfall below 1 mm. According to observations at the station in Prague-Klementinum, November 2011 was the driest November since 1804, which is the entire period of continuous rainfall measurement in this station.

Data sources

The Czech Hydrometeorological Institute

Links to additional information

Information about climate on the Czech Hydrometeorological Institute’s website
The Czech Hydrometeorological Institute’s Department of Climate Change
The World Meteorological Organization
The European Environment Agency