Europe ERA5 Climate Tracker

Domain and source data

Dataset

ECMWF Reanalysis v5 (ERA5)

Spatial domain

30°–72° N, 25° W–40° E

CDS grid

0.25° × 0.25°; 44,109 grid points

Data coverage

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The tracker uses ERA5 hourly data on single levels from the Copernicus Climate Change Service (C3S) Climate Data Store. ERA5 is a global reanalysis: a historical reconstruction of the atmosphere produced by repeatedly running a modern weather model over past decades while continuously incorporating observations from satellites, weather stations, balloons, aircraft, ships and other observing systems. This provides a spatially and temporally complete estimate of how atmospheric conditions evolved, including in places and periods where direct observations are sparse. ERA5 is produced with the ECMWF Integrated Forecasting System (IFS) and four-dimensional variational data assimilation (4D-Var), which combines these observations with the numerical model to reconstruct a physically consistent atmospheric state through time.

2 m air temperature. This is the estimated air temperature two metres above the model surface and is available across both land and sea. In the IFS it is a diagnostic screen-level quantity rather than the temperature of a model level: it is derived from the temperature at the lowest atmospheric model level and the underlying surface skin temperature using boundary-layer stability information. The hourly 2 m temperature distributed through the ERA5 Climate Data Store is an analysed parameter, so it is consistent with the observation-constrained atmospheric state produced by the reanalysis.

Sea surface temperature (SST). ERA5 SST is a prescribed foundation sea surface temperature rather than a prognostic temperature generated by the atmospheric model. Before September 2007 it is based on HadISST2; from September 2007 onward it is based on the Met Office OSTIA analysis. The ERA5 SST represents a foundation temperature without a resolved daytime solar-warming cycle. Although the field is available at hourly timestamps, its SST content is updated once per day.

Total precipitation. ERA5 total precipitation is the accumulated water-equivalent depth from rain and snow. This tracker reports precipitation in millimetres.

Mean sea-level pressure (MSLP). The optional pressure contours show ERA5 MSLP at 12:00 UTC on the selected date and are intended as an informative synoptic overlay. They provide a snapshot of the large-scale pressure pattern, but the underlying temperature fields are daily means and precipitation is accumulated over the daily period, so the combined display is not fully synoptic.

ERA5 values are reanalysis estimates rather than direct weather-station observations. Apparent local records or other extremes that are important for a specific application should therefore be checked against observations and, where appropriate, other climate datasets.

Data availability. Recent data are initially provided by C3S as preliminary ERA5T and are typically available about five days behind real time, with no guaranteed release time. This tracker updates daily and normally operates about six days behind real time. C3S subsequently replaces ERA5T with final ERA5 data, normally about two months later, so values from the most recent months should be regarded as preliminary.

Data citation: Hersbach H, Bell B, Berrisford P, et al. ERA5 hourly data on single levels from 1940 to present. Copernicus Climate Change Service Climate Data Store. doi:10.24381/cds.adbb2d47. For broader background on reanalysis, see Advancing Reanalysis.

Copernicus attribution and disclaimer. Contains modified Copernicus Climate Change Service information 2026. The European Commission and ECMWF are not responsible for uses made of the Copernicus information or data presented on this page.

Figure licence. Figures generated by this tracker may be reused and adapted under the Creative Commons Attribution 4.0 International licence (CC BY 4.0) , including for commercial purposes, provided that XpertScientific is credited and the ERA5/Copernicus data-source attribution is retained or otherwise provided. If a figure is modified, the modification should be indicated.

How the tracker is calculated

Daily temperature. Daily temperature means are calculated from the 24 hourly values from 00:00 through 23:00 UTC. The 2 m air temperature requires all 24 hours, while SST is retained only for complete valid days.

Daily precipitation. Daily total precipitation for calendar date D combines D 01:00–23:00 UTC with D+1 00:00 UTC. Since the ERA5 record for 1 January 1940 only contains 18 hourly values, the daily precipitation series begins on 2 January 1940.

Seasons and complete periods. Annual values refer to calendar years. Winter (DJF) is assigned to the year containing January and February; because December 1939 is outside the archive, complete winters begin in 1941. Incomplete years or seasons are excluded where complete-period statistics are required.

Full-domain values. Grid cells are weighted by physical area using the cosine of latitude. Air temperature and precipitation include both land and ocean, while SST is additionally weighted by the fractional ocean area from the ERA5 land–sea mask. Calculations use the original ERA5 grid; displayed map interpolation does not affect reported values, anomalies, rankings or trends.

Long-term trends. Trends use complete annual or seasonal values: mean temperature for air temperature and SST, and accumulated totals for precipitation. At least 25 complete years are required. Trends are estimated by ordinary least squares and reported in °C/decade for temperature and mm/decade for precipitation. Uncertainty is calculated using Newey–West HAC standard errors with Bartlett weights, L = floor[4(n/100)^2/9], and the n/(n−2) correction. The chart shows the fitted trend and pointwise 95% confidence interval; p is the two-sided HAC Wald p-value and R² is the conventional OLS value.

Map display. Map rasters are bilinearly interpolated between 0.25° cells for display only. For SST, interpolation is weighted by ocean fraction and pixels with less than 50% ocean coverage are transparent. Map clicks select the nearest ERA5 grid point.

Temperature

Historical comparison and daily anomalies. Historical comparisons are calculated separately for each calendar date. The chart shows the median and 10th–90th percentile range for the selected years, using either daily values or 7- or 15-day trailing means. Temperature views also show the 1991–2020 WMO climatological mean. Daily temperature anomalies are calculated relative to the same calendar date in the selected 30-year baseline; 29 February is treated separately using leap years.

Year-to-date temperature anomaly. The year-to-date value is the mean of daily temperature anomalies from 1 January through the selected date. Rankings include years with at least 90% valid coverage through the same calendar date.

Annual and seasonal temperature. Maps show either the absolute mean temperature for a complete year or season, or its anomaly relative to the corresponding mean for the selected 30-year baseline. Standardized anomalies divide this anomaly by the sample standard deviation (n−1) of the corresponding baseline means and are expressed in SD. Standardized maps use the smallest symmetric range among ±3, ±4, ±5, ±6 and ±8 SD that contains the 99th percentile of |z|.

Temperature heatmaps. Heatmaps show the available temperature record at daily or monthly resolution. Monthly values are means of the available daily values within each calendar month. Anomalies use the selected 30-year baseline; standardized anomalies divide each daily or monthly anomaly by the corresponding baseline sample standard deviation. Anomaly colour scales are symmetric around zero and based on the 99th percentile of absolute anomalies.

Precipitation

Cumulative year-to-date precipitation. The selected 30-year baseline defines the arithmetic-mean normal, median and 10th–90th percentile envelope. On 29 February, leap years contribute through 29 February and non-leap years through 1 March, so every baseline year represents the same 60 elapsed days. YTD values and rankings begin in 1941.

Monthly, seasonal and annual precipitation. These views show accumulated precipitation totals. Absolute anomalies are the observed total minus the arithmetic-mean total for the selected 30-year baseline, in millimetres. Percentage of normal is shown separately as 100 × actual / normal and is not an anomaly. January and annual 1940 include the available 18 hours from 1 January together with the remainder of the period and remain included in climatologies and rankings.