The ground-based World-Wide Lightning Location Network (WWLLN) has continuously monitored global lightning since 2004.  We are pleased to make available monthly stroke density time series derived from WWLLN lightning detections.  The number of WWLLN stations has been largely consistent since 2013, so stroke density data are available for 2013-present.

What is stroke density?

Stroke density is the number of strokes detected at a particular location during a time period—that is, how much lightning is occurring.  For this dataset, strokes are counted on a 0.1° or 1° latitude/longitude grid during each month.

These stroke densities are as detected by WWLLN and are not corrected for relative detection efficiency, which varies with time and location.  Comparisons between absolute intensities in different continental regions, using this work, could be misleading.


Monthly stroke density for the full period of record, illustrating both seasonal and interannual variability.

Stroke density over the Arctic, outside the field of view of geostationary lightning sensors:  yearly animation and climatological-mean plot for May-September.

Data access

The WWLLN monthly stroke density dataset is available for research (i.e., non-commercial) use.  Further information about the dataset can be found in the readme.  When using the data, please include the following statement:  “The authors wish to thank the WWLLN (http://www.wwlln.net), a collaboration among over 50 universities and institutions, for providing the lightning data used in this paper.”


Please send questions to Katrina Virts or Bob Holzworth.