At IMWM-PIB, similarly to other meteorological centers around the world, the average monthly air temperature/monthly total precipitation for a given month is forecast in relation to the long-term standard adopted for the period 1991-2020. The average monthly temperature/monthly precipitation values for this 30-year period are sorted from lowest to highest, with the 10 lowest values being the average temperature/precipitation in the "below normal" class, the middle 10 being "normal" and the 10 highest being "above normal" ".
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Weather forecast for July 10 and 11
What do the terms "above normal", "below normal" and "within normal" mean?
When average temperature/precipitation is expected:
– above the norm, it can be assumed that the forecast month will be warmer/wetter than at least 20 observed, the same months in the years 1991-2020,
– below normal, it can be assumed that the forecast month will be colder/drier than at least 20 observed, the same months in 1991-2020,
– the norm assumes that the forecast month will be similar to the typical 10 observed months in the years 1991-2020.
Please note that the forecast average temperature refers to the average temperature of the entire month, both during the day and at night. The forecast rainfall refers to the sum of rainfall from all days in the month. The type of precipitation (snow or rain) is not specified in the forecasts.
When preparing the final monthly forecast, IMWF-PIB uses its own IMWM-Reg and IMWM-Bayes models as well as the results of NOAA (National Oceanic and Atmospheric Administration) and ECMWF (European Center for Medium-Range Weather Forecasts) models.
Why are long-term forecasts subject to great uncertainty and may differ from each other?
Despite the increasing computing power of supercomputers and extensive knowledge of weather processes, it is still impossible to avoid errors and differences in forecasts for such a long period into the future. They result both from the risk of sudden (often local) meteorological phenomena that may disturb the forecast weather processes, and from the sheer diversity of physical assumptions and mathematical and statistical equations used in forecasting models. It is not possible to provide a more accurate description of the weather forecast this far in advance. Please remember that the forecast is indicative, experimental in nature and concerns the average course for the entire forecast region and a given forecast period.
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There are growing concerns among farmers about this year's grain yields
August 2024 – long-term temperature and precipitation forecast
Throughout the country, the average monthly air temperature will most likely be above the long-term norm from 1991-2020. The monthly amount of precipitation should be within the long-term norm.
Source: IMWM
Source: IMWM 
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We know the exact date of payment of cereal subsidies. A correction factor will be applied
September 2024 – long-term temperature and precipitation forecast
Throughout Poland, the average monthly air temperature should be above the long-term norm from 1991-2020. The monthly rainfall total will most likely be within the long-term norm.
IMGW_0710 Annex 3.png
Source: IMWM
October 2024 – long-term temperature and precipitation forecast
The average monthly air temperature should be within the range of the long-term norm from 1991-2020. The monthly rainfall total will most likely be above the long-term norm.
Source: IMWM
Source: IMWM
November 2024 – long-term temperature and precipitation forecast
Throughout Poland, the average monthly air temperature should be within the range of the long-term norm from 1991-2020. The monthly rainfall total will most likely be above the long-term norm.
Source: IMWM
Source: IMWM
