The files wtr.csv and wtr.header contain the data and their semantics of the so-called weather data set used in:
   Magnus Mueller, Guido Moerkotte, and Oliver Kolb.
   Improved selectivity estimation by combining knowledge from sampling and synopses.
   Proceedings of the VLDB Endowment 11.9 (2018): 1016-1028.


The data set is a relation that contains around 3.4 million tuples.
The 7 attributes of the relation have the following meaning:
   - latitude,
   - longitude,
   - altitude (-999.9 means unknown),
   - day of year,
   - minimum temperature,
   - maximum temperature (some cases where min temperature > maxtemperature),
   - and precipitation (in tenth of mm)


The relation contains processed data from the daily global historical climatology network by:
   M. Menne, I. Durre, B. Korzeniewski, S. McNeal, K. Thomas, X. Yin, S. Anthony, R. Ray, R. Vose, B. Gleason, et al.
   Global historical climatology network-daily (ghcn-daily), version 3.
   NOAA National Climatic Data Center, 2012.
   
   M. J. Menne, I. Durre, R. S. Vose, B. E. Gleason, and T. G. Houston.
   An overview of the global historical climatology network-daily database.
   Journal of Atmospheric and Oceanic Technology, 29(7):897-910, 2012.

A selection of their data was joined and projected. In addition, the data set was extended by the "day of year" attribute.