In this article · 8 sections
WeatherSTEM and Flash sell to many of the same people: athletic directors, school administrators and venue safety managers. WeatherSTEM alerts when lightning is detected inside a zone you draw, and sells weather stations and outdoor sirens to go with it. Flash forecasts lightning for every square kilometre before it strikes, with nothing to install. This comparison sets out what each publishes, as of 17 October 2026.
The short answer
WeatherSTEM’s Lightning Platform sends instant lightning detection alerts by SMS, email or voice for notification zones you draw as rings or custom shapes, with all-clear signals after the storm and no hardware required; its outdoor warning system adds sirens and beacons. Flash forecasts, for every 1×1 km cell, the likelihood of a cloud-to-ground strike in the next 60 minutes, refreshed every 2 minutes, with up to 99.6% one-hour accuracy scored against NLDN strikes. Choose WeatherSTEM if you want detection alerts plus an on-site station and siren from one supplier. Choose Flash if you want the warning before the first strike.
What WeatherSTEM does well
Everything in this section is as published on weatherstem.com, checked 17 Oct 2026: the Lightning Platform page (opens in a new tab), the lightning detection page (opens in a new tab), the weather station and outdoor warning page (opens in a new tab) and an older safety page (opens in a new tab) (© 2022).
- Built for schools and venues. WeatherSTEM says athletic directors and school administrators rely on it to protect students and to adhere to NFHS and NCAA rules, and that safety managers in schools, event venues, logistics hubs and government agencies use it.
- Zones you draw. Notification zones can be tailored rings or custom-shaped areas drawn with its mapping tools.
- Coverage. The current page says WeatherSTEM uses dual lightning data providers so there are no gaps in coverage.
- Fast to start, nothing to install. No hardware is needed for the platform, and WeatherSTEM says customers are fully operational in less than 24 hours.
- Simple delivery. Alerts arrive by SMS, email or voice, with no login or app needed to open them, and all-clear signals are sent after the storm.
- Optional on-site hardware. Its outdoor warning system offers high-output directional alarms, either sirens or text-to-speech, and flashing beacons, for venues such as schools, sports stadiums and parks; WeatherSTEM says its detection system connects directly to it.
- Heat. The older safety page says WeatherSTEM units have the inputs to compute WBGT, and that it offers a WBGT forecast model.
How Flash approaches the same problem
A detection alert fires on lightning that has already been detected inside your zone. It is quick, it confirms the storm, and it anchors the all-clear clock. It cannot warn before a storm’s first strike in your zone, because the alert starts with a strike. Flash forecasts from the other direction: it ingests 30+ integrated data signals, including radar, satellite and surface observations, and outputs a likelihood of a cloud-to-ground strike over the next 60 minutes for every 1×1 km cell across the continental U.S., refreshed every 2 minutes.
- 60 minlead time, up to
- 1×1 kmcell per site
- 2 minmodel refresh
- Up to 99.6%one-hour lightning accuracy
Because a forecast can be wrong, Flash scores it like one: hit or miss per cell on the one-hour window, against an independent record of NLDN strikes. The definitions are on the accuracy method page. WeatherSTEM describes its data as refreshed at a sub-second rate; we did not find a published accuracy percentage or scoring method on the pages we checked, so ask for one.
Flash runs in the web app, the mobile app, SMS and email, and drives horns and strobes you already own through relays. Where you want a new siren that sounds on the forecast, Flash Weather Shield is solar-powered and cellular. For heat, a 6-hour WBGT outlook plans alongside any on-site reading your policy requires.
WeatherSTEM vs Flash, side by side
| Attribute | WeatherSTEM | Flash |
|---|---|---|
| What triggers a lightning alert | Lightning detected inside a notification zone you draw | A forecast for your 1×1 km cell, up to 60 minutes before the first strike |
| All-clear | All-clear signals sent after the storm | All-clear timer after the last strike |
| Accuracy | No percentage or method found on the pages we checked | Up to 99.6% one-hour accuracy against NLDN strikes; method published |
| Delivery | SMS, email or voice; no login or app needed | Web app, mobile app, SMS and email |
| Hardware | None required; optional weather stations and outdoor sirens and beacons | None required; relays for existing horns, or Flash Weather Shield |
| Heat | Station inputs for WBGT and a WBGT forecast model (older page) | 6-hour WBGT outlook beside any on-site reading |
| Pricing | Not published on the pages we checked | Per site, annual, quoted after a demo; free app tier for individuals |
WeatherSTEM
- What triggers a lightning alert
- Lightning detected inside a notification zone you draw
- All-clear
- All-clear signals sent after the storm
- Accuracy
- No percentage or method found on the pages we checked
- Delivery
- SMS, email or voice; no login or app needed
- Hardware
- None required; optional weather stations and outdoor sirens and beacons
- Heat
- Station inputs for WBGT and a WBGT forecast model (older page)
- Pricing
- Not published on the pages we checked
Flash
- What triggers a lightning alert
- A forecast for your 1×1 km cell, up to 60 minutes before the first strike
- All-clear
- All-clear timer after the last strike
- Accuracy
- Up to 99.6% one-hour accuracy against NLDN strikes; method published
- Delivery
- Web app, mobile app, SMS and email
- Hardware
- None required; relays for existing horns, or Flash Weather Shield
- Heat
- 6-hour WBGT outlook beside any on-site reading
- Pricing
- Per site, annual, quoted after a demo; free app tier for individuals
When WeatherSTEM is the better fit
- Your policy is written around detected lightning inside a zone, and you want alerts that need no app or login.
- You want a weather station and an outdoor siren from the same supplier as your alerts.
- You want to draw custom-shaped zones around a campus or venue.
When Flash is the better fit
- You need to start clearing fields before the first strike, not after it.
- You want every field, pool or course judged on its own 1×1 km cell.
- You want a published, checkable accuracy method behind the alert.
Flash is a Preferred Vendor Partner across all 700+ Troon golf properties, the official weather safety provider of the Big 12 Conference, and the Official Weather Monitoring & Alert System of the NAIA through October 2028.
Running both
Detection and a forecast do different jobs and can share one written policy: the forecast to start moving people, detection to confirm the storm and run the all-clear clock. The lightning safety policies guide shows what NFHS, NCAA and state associations ask of a school, and the vendor comparison hub sets WeatherSTEM beside the other tools we have compared.
Frequently asked
WeatherSTEM describes its Lightning Platform as instant lightning detection and alerts, sent when lightning is detected inside a zone you set, as its site shows on 17 Oct 2026. Flash forecasts the likelihood of a strike per 1×1 km cell for the next 60 minutes.
Neither requires it. WeatherSTEM says its lightning platform needs no hardware, and sells optional weather stations and outdoor sirens. Flash needs none, drives existing horns through relays, and offers Flash Weather Shield as an optional siren.
Yes. Keep detection alerts for confirmation and the all-clear, and add Flash for the hour before the first strike. Write both into the lightning section of your emergency action plan.