Lightning FAQ: What are lightning strike maps?

By DAN ROBINSON
Editor/Photographer

Lightning strike maps are images that display the locations where cloud-to-ground lightning strikes have occured.

Today, private companies and open-source groups operate networks of special sensors that can detect radio waves produced by lightning. These radio waves are used to calculate how far away a strike is in relation to the sensor. The data collected by multiple sensors allows the location of strikes to be calculated via triangulation. This data is used to create detailed maps of lightning strikes on a real-time basis. Ground strike points on the maps are marked with dots, plus signs (for positive-flash strikes), or minus signs (for negative-flash strikes).

Although comprehensive access to lightning data is generally fee-based, there are many free lightning data sources on the internet, many of them real-time (or slightly delayed).

Free online data sources

Blitzortung: This is an open-source network consisting of home-built sensors that originally started overseas. It's the lightning equivalent of amateur weather stations providing data to sites like Weather Underground. It now has lightning data for the US, and the data is accurate and up-to-date. I use this source daily! The plans for making the devices are free, but to get a sensor, currently you must build it yourself from sratch. You really don't need a sensor right now if you live in the USA and most of Europe, as there are plenty of them operating now to provide good data. More volunteers building sensors will help the network's accuracy improve, however - I plan to do it at some point.
Here are the ways to view Blitzortung data:
- Full USA Web Map: This is a non-zoomable map of lightning strike data in the USA. While it can't be zoomed, it is the most 'lightweight' of the sources in terms of browser resources.
- Zoomable Web Map: This map is good if you want to zoom into a specific area. The audio 'ticks' will only sound for strikes that happen in the visible map area, useful if you want to keep a browser window open and be alerted of storms that are producing lightning within a specific area. This map is more resource-intensive, and has a tendency to crash now and then in some browsers.
- Android and iOS apps: Blitzortung has free apps available that are quite useful, in that they have alarms that can be configured to go off if lightning happens within a set range of your GPS location. The apps are still a little buggy, and the map views don't work well. Right now I use the above web sites for map viewing, and use the app on my tablet as a lightning alarm that will even wake me up if storms are firing in my area.
Vaisala: Vaisala is the owner of the original NLDN (National Lightning Detection Network). Their data has generally been tailored for business and government clients, and their prices have been out of range for the average casual user. Their free map is delayed by at least 20 minutes, limiting its usefulness - but it is a good backup for monitoring lightning trends. Now that Blitzortung is online in the US, I rarely use this link.

Fee-based services that include lightning data

(The listing of these services are neither paid nor constitute an official endorsement)

Radarscope: Radarscope is a mobile app that has an option for lightning data to be added on. At last report, the app cost $9.95 to buy (one time charge), with the lightning data an additional $9.95 per year. I have heard good reviews of this app, but have never used the lightning data option myself since I currently operate WxWorx.
Baron/XM WxWorx (Mobile Threat Net): I have been using the WxWorx system continuously since 2004. The median-level and top-level plans include realtime lightning data. WxWorx is only an option for the most serious of storm observers due to its cost. I use it because it is satellite-based and therefore always works no matter where I am - I do not lose data if I don't have a cellular signal.