What the checker actually does
The site uses a deterministic regional ruleset. It does not ask an AI model to invent a forecast. A city or ZIP is resolved to a U.S. state, the state is mapped to a climate region, and the result combines two different evidence layers: the current NOAA Climate Prediction Center seasonal outlook and historical El Niño tendencies.
Why temperature, precipitation and snow are separate
Snow requires both moisture and sufficiently cold air. A wetter seasonal signal can produce more rain instead of more snow when temperatures run mild. That is why the site never converts “wet” directly into “snowy.”
How we label confidence
Confidence reflects how coherent the large-scale signal is for the region—not the chance that a specific day will match it. A high-confidence seasonal wet signal can still contain dry weeks. A warm-tilted winter can still produce severe cold snaps.
Current versus historical evidence
The current layer uses the embedded September 2026 ENSO and August 2026 long-lead CPC outlook. The historical layer uses NOAA Climate.gov analyses of past El Niño temperature, precipitation and snowfall patterns. When the two disagree, the checker lowers confidence or uses “mixed.”
Freshness guard
The embedded snapshot is dated. If it becomes older than 35 days, the checker automatically displays a stale-data warning and directs the user to NOAA. This prevents an old seasonal snapshot from quietly presenting itself as current.
What the checker deliberately does not do
- No storm-by-storm prediction.
- No exact snowfall totals months in advance.
- No claim that a very strong El Niño guarantees a local outcome.
- No safety verdict for travel, driving, flooding, skiing or outdoor activities.
- No automatic use of the user’s GPS location.
How location matching works
The checker needs only a state-level climate region. City/state text is parsed locally; major U.S. cities have a small built-in convenience lookup, while other cities should include a state abbreviation. Five-digit ZIP codes are mapped to a state using an embedded federal ZIP-prefix table and known exceptions. This is intentionally not street-level geocoding.