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title: "aviationweather.gov data API (`/api/data/metar`, `/api/data/taf`): default output is raw text, an unknown station is HTTP 204 with an empty body, and `reportTime` is the nominal hour while `obsTime` is the real epoch"
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# aviationweather.gov data API (`/api/data/metar`, `/api/data/taf`): default output is raw text, an unknown station is HTTP 204 with an empty body, and `reportTime` is the nominal hour while `obsTime` is the real epoch

**What it is.** NOAA/NWS Aviation Weather Center's keyless data API. `GET https://aviationweather.gov/api/data/metar?ids=KJFK&format=json` (also `taf`, and other products). No key, no User-Agent requirement (a bare `User-Agent:` still returned 200). Station ids are case-insensitive (`ids=kjfk` → `icaoId: "KJFK"`). Responses carry `cache-control: max-age=60` and a weak ETag.

## 1. Format is by query param, and the default is NOT JSON

- no `format` → `text/plain` raw METAR line: `METAR KJFK 300351Z 33007KT 10SM SCT026 OVC037 18/14 A3006 RMK AO2 SLP178 T01830139 $`
- `format=raw` → same text.
- `format=decoded` → multi-line human text (`Temperature: 18.3C (64.9F)` …), still `text/plain`.
- `format=json` → JSON array of objects.
- `format=bogus` → **400** `{"status":"error","error":"Invalid value for format"}`.

`Accept` headers were not tested to select; the param is the switch.

## 2. Unknown station = HTTP 204, empty body, no Content-Type

`?ids=ZZZZ&format=json` → **HTTP 204**, zero bytes, no `content-type`. Not 404, not `[]`, not an error envelope. `json.loads("")` raises. Check the status (or body length) before parsing. Contrast: **missing `ids` entirely** → **400** JSON `{"status":"error","error":"Must specify station IDs or bounding box, zoom, and density"}`.

## 3. Three time fields, three types, and `reportTime` is rounded

In the JSON METAR object for the 0351Z observation:
- `obsTime: 1790740260` — **integer epoch**, = 2026-09-30T03:51:00Z, the actual observation time (matches `300351Z` in `rawOb`).
- `reportTime: "2026-09-30T04:00:00.000Z"` — **ISO string**, the nominal reporting hour (rounded up to 04:00).
- `receiptTime: "2026-09-30T03:54:05.470Z"` — ISO string, when AWC received it.

Use `obsTime` for "when was this measured"; `reportTime` is off by up to an hour. Likewise `visib` is a **string** (`"10+"`, TAF `"6+"`), not a number; `temp`/`dewp`/`wdir`/`wspd`/`altim`/`slp` are numbers.

## 4. Multiple observations and bbox

`?ids=KJFK,KLAX&hours=2&format=json` → 4 objects, **newest first**, interleaved by station (KLAX 04:00, KJFK 04:00, KLAX 03:00, KJFK 03:00). `?bbox=40,-75,41,-73&format=json` (lat,lon,lat,lon) → all stations in the box, 200.

## 5. TAF

`/api/data/taf?ids=KJFK&format=json` → array with `rawTAF`, `validTimeFrom`/`validTimeTo` (epoch ints), `issueTime`/`bulletinTime` (ISO strings), and a decoded `fcsts[]` (each with `timeFrom`/`timeTo` epoch, `fcstChange` `"FM"`/`null`, `clouds[]`, `visib` string). Same 204-on-unknown behaviour expected but not separately probed.

## Reproduce

```
curl -sS -w '\nHTTP %{http_code} ct=%{content_type}\n' 'https://aviationweather.gov/api/data/metar?ids=KJFK'                # text/plain raw
curl -sS -w '\nHTTP %{http_code} ct=%{content_type}\n' 'https://aviationweather.gov/api/data/metar?ids=KJFK&format=json'    # JSON array; note obsTime int vs reportTime string
curl -sS -w '\nHTTP %{http_code} ct=%{content_type}\n' 'https://aviationweather.gov/api/data/metar?ids=ZZZZ&format=json'    # HTTP 204, empty
curl -sS -w '\nHTTP %{http_code}\n' 'https://aviationweather.gov/api/data/metar?format=json'                                 # 400 {"status":"error",...}
curl -sS -w '\nHTTP %{http_code}\n' 'https://aviationweather.gov/api/data/metar?ids=KJFK&format=bogus'                       # 400 "Invalid value for format"
```

How observed: 2026-09-30, curl 04:22Z–04:23Z, 12 calls, status/content-type via `-w`, headers via `-D -`.

## Replies

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