weather.us.forecast

US Weather Forecast

The official National Weather Service forecast for a US coordinate — six 12-hour periods by default, or hourly — compact unless detail=full is requested, with the issue time so an agent can judge its age.

Example answer

Ask

What is the weather forecast for these US coordinates?

GET /v1/weather/us/forecast?lat=38.8977&lon=-77.0365

Eckari

{
  "query": {
    "lat": 38.8977,
    "lon": -77.0365,
    "hourly": false,
    "period_limit": 6,
    "hours": null,
    "detail": "compact"
  },
  "location": {
    "city": "Washington",
    "state": "DC",
    "timezone": "America/New_York"
  },
  "updated_at": "2026-08-18T13:16:54.000Z",
  "generated_at": "2026-08-18T16:05:18.000Z",
  "valid_from": "2026-08-18T07:00:00.000Z",
  "periods": [
    {
      "name": "This Afternoon",
      "start_time": "2026-08-18T12:00:00-04:00",
      "end_time": "2026-08-18T18:00:00-04:00",
      "is_daytime": true,
      "temperature_c": 31.11,
      "temperature_f": 88,
      "precipitation_probability_pct": 11,
      "wind_speed_range_kmh": {
        "min": 11.27,
        "max": 11.27
      },
      "wind_direction": "N",
      "short_forecast": "Partly Sunny"
    },
    {
      "name": "Tonight",
      "start_time": "2026-08-18T18:00:00-04:00",
      "end_time": "2026-08-19T06:00:00-04:00",
      "is_daytime": false,
      "temperature_c": 21.67,
      "temperature_f": 71,
      "precipitation_probability_pct": 1,
      "wind_speed_range_kmh": {
        "min": 1.61,
        "max": 9.66
      },
      "wind_direction": "NW",
      "short_forecast": "Partly Cloudy"
    },
    {
      "name": "Wednesday",
      "start_time": "2026-08-19T06:00:00-04:00",
      "end_time": "2026-08-19T18:00:00-04:00",
      "is_daytime": true,
      "temperature_c": 32.22,
      "temperature_f": 90,
      "precipitation_probability_pct": 0,
      "wind_speed_range_kmh": {
        "min": 8.05,
        "max": 8.05
      },
      "wind_direction": "W",
      "short_forecast": "Sunny"
    }
  ]
}

Source: National Weather Service
Freshness: Near live
Price: $0.003

Version: 4.0.0
Transport: HTTP / MCP
Coverage: US

Use this when

What is the weather forecast for these US coordinates?
Will it rain in Washington DC tomorrow?
You need an hourly US forecast for the next 24-48 hours.
You need the official NOAA/NWS forecast rather than a modelled aggregation.
You need forecast temperatures and wind for a US delivery, event or site visit.
You need the forecast issue time for provenance.

Don't use this when

You need the latest observed conditions and their age - use weather.us.observation.
You need active warnings, watches or advisories - use weather.us.alerts.
The location is outside the United States and its territories (returns UNSUPPORTED_REGION).
You need historical or climate data, radar imagery or model output - not supported.

If the user has asked you to inspect a specific website, page or URL, use your browsing tool instead — this capability only returns the US National Weather Service API record.

Input

latnumberrequired

Latitude in decimal degrees (WGS84). Rounded to 4 decimal places before the National Weather Service lookup.

lonnumberrequired

Longitude in decimal degrees (WGS84). Rounded to 4 decimal places before the National Weather Service lookup.

hourlybooleandefault false

Return hourly periods instead of the default 12-hour day/night periods. Hourly periods have no name and, at detail=full, carry dewpoint and humidity.

period_limitintegerdefault 6

Maximum number of 12-hour day/night periods to return, soonest first. Applies when hourly is false; use hours for hourly forecasts. NWS issues 14 periods (7 days); the default of 6 is three days. Named period_limit, not periods, because periods is the returned series.

hoursintegerdefault 24

Number of hourly periods to return, soonest first. Applies when hourly is true; use period_limit for day/night forecasts.

detailstringdefault "compact"

compact (default) returns the fields an agent acts on. full adds the NWS narrative (detailed_forecast), the icon URL, the trend note and, for hourly periods, dewpoint_c and humidity_pct.

What the result means

queryobject

The request as resolved, echoed so a batched caller can match answers to inputs and see which defaults were applied.

locationobject

What the National Weather Service reports at the queried point. The coordinates are in query; the forecast office and grid square that produced the forecast are provenance, not weather, and are not published here - meta.source names the provider.

updated_atstring, null

Time the forecast product was issued by the forecast office (NWS updateTime), RFC 3339 UTC. This is the true age of the forecast.

generated_atstring, null

Time NWS generated this response from the forecast grid (RFC 3339 UTC).

valid_fromstring, null

Start of the validity interval of the underlying forecast grid (RFC 3339 UTC).

periodsarray

Forecast periods in chronological order, soonest first, as issued by the forecast office. This is a time series, not a paged list - ask for more with periods or hours.

Provenance

Source: National Weather Service
Freshness: Near live · read at request time, not cached
Region: US

Access

Over MCP: weather_us_forecast
Over HTTP: GET https://api.eckari.com/v1/weather/us/forecast
Price: $0.003 per call over x402. Account access $0.002 when that rail opens.