Thunderstorm Probability (Core Feature, Included)

The Thunderstorm Probability parameter provides the probability of thunderstorm activity at a given location and time.

How this probability should be interpreted depends on the forecast region and timeframe. Within the continental United States (CONUS), Thunderstorm Probability provides a standalone thunderstorm probability forecast for the first 36 hours.

Beyond 36 hours within CONUS, and for forecasts outside CONUS, Thunderstorm Probability is precipitation-dependent.

Understanding this distinction is important when using Thunderstorm Probability for monitoring, insights, or alerts.

🌐 This feature is part of Tomorrow.io’s core data offering and is available to all platform and API users.

How Thunderstorm Probability Works

Forecast Coverage

NextGen CONUS

• Available up to 36 hours ahead.
• Represents the likelihood of thunderstorms occurring at a given location and time.
• Calculated independently of whether precipitation is forecast.
• Best suited for short-range thunderstorm monitoring and alerting within CONUS.

Beyond 36 Hours and Non-CONUS

• Provides longer-range thunderstorm guidance, including forecasts out to approximately 14 days where available.
• Represents the probability of thunderstorms if precipitation develops.
• Should be interpreted together with the precipitation forecast.

For example, a high Thunderstorm Probability in a Classic or non-CONUS forecast does not necessarily mean a thunderstorm is likely if the forecast has low confidence that precipitation will occur.

Note: Thunderstorm Probability is a forecast parameter and should not be interpreted as an observation of thunderstorms or lightning currently occurring at a location.

Best Practices for Insights and Alerts

Within CONUS and the first 36 hours of the forecast, use Thunderstorm Probability as the primary forecast signal when configuring thunderstorm-based alerts.

Beyond 36 hours within CONUS, and for locations outside CONUS, consider combining Thunderstorm Probability with a precipitation threshold.

For example:

Thunderstorm Probability > 50% AND Precipitation Intensity > 1 mm/h

This helps account for both the potential for thunderstorms and the likelihood that meaningful precipitation will develop.

Note: Thresholds should be configured according to your organization's operational requirements and tolerance for weather risk.

Choosing Between Storm Prediction Tools

Use Thunderstorm Probability when your primary concern is thunderstorm development.

If your operation is specifically focused on lightning, or you need additional short-term situational awareness, another storm prediction tool may be more appropriate.

See Choosing the Right Storm Prediction Tool for guidance on Thunderstorm Probability, Lightning Probability, Lightning Nowcast, and Lightning Clusters.

Visualization

• Use the map view and timeline to track thunderstorm probabilities across time and regions.
• For post-36h and non-CONUS forecasts, probability is expressed as a percentage representing the chance that lightning flash density will exceed 0.1 flashes per 100 km² per hour.

Platform & API Access

• Available on the Tomorrow.io platform (map and timeline).
• Accessible via the API. Refer to API Documentation for integration guidance.

Important Notes

• The thunderstorm probability layer is distinct from real-time Lightning Alerts, which remain the primary tool for short-term operational decisions.
• This product is best used for regional outlooks, not pinpoint strike predictions.
• Post-36h and non-CONUS forecasts are updated every 12 hours.
• For post-36h and non-CONUS forecasts, data is provided in 3-hour intervals and switches to 6-hour intervals after +144 hours.

Need Help?

For questions or support, contact us at support@tomorrow.io or reach out to your Account Team.