NWS Watches, Warnings & Advisories
The National Weather Service issues watches, warnings, and advisories for hazardous weather conditions across the US. LMKwhen monitors these alerts in near real-time and notifies you when your location falls within an affected area.
Watch vs. Warning vs. Advisory
| Type | Meaning | Lead time |
|---|---|---|
| Watch | Conditions are favorable for the hazard to develop | Hours to days |
| Warning | Hazard is imminent or occurring — take action now | Minutes to hours |
| Advisory | Less serious conditions that may cause inconvenience | Varies |
How LMKwhen monitors NWS alerts
NWS alerts are polygon-based — each alert covers a specific geographic area. LMKwhen checks whether each of your locations falls within that polygon. If it does, an alert fires.
This check runs continuously. New NWS alerts typically appear in LMKwhen within 2–5 minutes of NWS issuance.
Common alert types
- Tornado Warning / Watch
- Severe Thunderstorm Warning / Watch
- Winter Storm Warning / Watch / Advisory
- Flood Warning / Advisory
- High Wind Warning / Advisory
- Freeze Warning / Watch
- Heat Advisory / Excessive Heat Warning
Alert lifecycle
When an NWS alert is issued that affects your location:
- LMKwhen fires an ACTIVE alert notification
- If the NWS alert is updated with a broader/worse condition, a new alert fires
- When the NWS alert expires, LMKwhen sends an all-clear notification and resolves the alert