ECA&D daily station data
The ECA&D dataset from KNMI consists of European daily station data. The coverage is a bit uneven, as some countries still are reluctant to freely share daily data (this is improving steadily). In January 2009 the dataset contained 979 precipitation series and 485 temperature series with lengths varying from 2 to 248 years.

The data is obtained from two main sources: the weather services and the GTS (Global Telecommunicaion System, the system used to exchange data to make weather forecasts). The latter is used to bring the series up-to-date, but is also notoriously unreliable, with many typos, misplaced decimal points, missing data etc. The majority of these errors are caught in the Quality Control, but some inevitably remain. The pure series do not include GTS data, the blended series do. The latter are therefore more up-to-date but less reliable.

The full ECA&D data can be obtained from their server. The data are updated daily there, the Climate Explorer makes a copy about once a month. The ECA&D server contains much more metadata than the Climate Explorer, which just tries to give a reasonable time series. These metadata indicate the averaging period (0-24 or 8-8 hours) and station relocations that could be associated with inhomogeneities.

Precipitation, temperature
These comprise the majority of the data in the datset, and in general have good quality.
Pressure
The pressure data are not well homogenised yet. The reduction to sea-level is also not uniform.
Cloud cover, snow depth
These variables ar relatively recent additions and do not yet have the level of quality control of the other data.
Relative humidity, sunshine duration
At the moment only available from the ECA&D website.