Thunderstorm Watch is a narrow US-English utility built to answer one urgent question clearly: is a place I care about under a Severe Thunderstorm Watch right now? The full manual ZIP answer is free and does not require a login or email address.
Source hierarchy
- National Weather Service data is canonical. It controls the national list and the ZIP-point result.
- Official NWS and SPC links and affected-area text provide the controlling detail.
- Iowa Environmental Mesonet geometry supplies broad SPC watch-box orientation only.
- Zippopotam resolves a five-digit ZIP to a centroid for the NWS point query.
No third-party weather source is allowed to overrule the NWS watch result.
Why failures are shown as unknown
A network response is not useful merely because it arrived. Thunderstorm Watch checks the official NWS update timestamp and treats a snapshot older than the freshness threshold as stale. If NWS or geocoding cannot be verified, the interface says it does not know and explicitly warns users not to interpret the failure as no active watch.
That fail-closed behavior is a core product rule and also governs future monitoring: stale or failed official data cannot generate an all-clear transition.
What the map means
The map is a progressive enhancement for national orientation. Public OpenStreetMap tiles are used only for the initial low-volume launch and are not assumed to be permanent high-volume infrastructure. If the map library, tiles, or IEM geometry fails, the official text list and ZIP checker remain useful.
A watch polygon or ZIP centroid is not an exact-address determination. Boundary cases should be checked against official county/zone text, local alerts, and weather.gov.
Not official and not a warning replacement
Thunderstorm Watch is not affiliated with or endorsed by NOAA, NWS, SPC, FEMA, or another government agency. It provides supplemental information only. Users must rely on Wireless Emergency Alerts, NOAA Weather Radio, local authorities, and weather.gov for life-safety decisions.
A Watch means severe storms are possible and people should prepare and stay informed. A Warning means dangerous weather is occurring or imminent and people should act on official instructions.
Project contact surface
This About page is the production contact URL used in the identifying User-Agent sent to the NWS API. Cloudflare transactional-email transport is configured for bounded account and future watch-state messages, but no public support mailbox is advertised. Production checkout remains disabled until the remaining legal/support launch gate is explicitly cleared.