diff --git a/src/reformatters/ecmwf/ecmwf_utils.py b/src/reformatters/ecmwf/ecmwf_utils.py
index 157b3f21e..d9a11dc2a 100644
--- a/src/reformatters/ecmwf/ecmwf_utils.py
+++ b/src/reformatters/ecmwf/ecmwf_utils.py
@@ -1,3 +1,4 @@
+import re
 from collections.abc import Callable, Sequence
 from pathlib import Path
 from typing import Literal
@@ -21,7 +22,15 @@ def ecmwf_download_with_fallback(
         try:
             return download_one(source)
         except FALLBACK_EXCEPTIONS as e:
-            log.warning(f"ECMWF download from {source!r} failed, will fall back: {e}")
+            detail = str(e)
+            if "404 Not Found" in detail:
+                url = re.search(r"https?://\S+", detail)
+                detail = f"{type(e).__name__}: 404 Not Found"
+                if url:
+                    detail += f" for {url[0]}"
+            log.warning(
+                f"ECMWF download from {source!r} failed, will fall back: {detail}"
+            )
             last_exc = e
     assert last_exc is not None
     raise last_exc
diff --git a/tests/ecmwf/ecmwf_utils_test.py b/tests/ecmwf/ecmwf_utils_test.py
new file mode 100644
index 000000000..2b28ff683
--- /dev/null
+++ b/tests/ecmwf/ecmwf_utils_test.py
@@ -0,0 +1,166 @@
+from collections.abc import Iterator
+from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
+from pathlib import Path
+from threading import Thread
+from unittest.mock import Mock, call
+
+import obstore
+import pytest
+from obstore.exceptions import GenericError, PermissionDeniedError
+from obstore.store import HTTPStore
+
+from reformatters.ecmwf.ecmwf_utils import (
+    EcmwfOpenDataSource,
+    ecmwf_download_with_fallback,
+)
+
+
+@pytest.fixture
+def missing_object_server() -> Iterator[str]:
+    class Handler(BaseHTTPRequestHandler):
+        def do_GET(self) -> None:
+            self.send_response(404)
+            self.end_headers()
+            self.wfile.write(b"<Error><Code>NoSuchKey</Code></Error>")
+
+        def log_message(self, format: str, *args: object) -> None:  # noqa: A002
+            pass
+
+    with ThreadingHTTPServer(("127.0.0.1", 0), Handler) as server:
+        thread = Thread(target=server.serve_forever)
+        thread.start()
+        try:
+            yield f"http://127.0.0.1:{server.server_port}"
+        finally:
+            server.shutdown()
+            thread.join()
+
+
+def _http_error_detail(url: str, status: str = "404 Not Found") -> str:
+    return (
+        f"Object at location forecast.index not found: Error performing GET {url}"
+        f" in 612.648µs - Server returned non-2xx status code: {status}:"
+        " <Error><Code>NoSuchKey</Code></Error>\n\nDebug source:\n"
+        'NotFound { path: "forecast.index", source: RetryError(...) }'
+    )
+
+
+@pytest.mark.parametrize("source", ["gcs", "s3"])
+@pytest.mark.parametrize("suffix", ["index", "grib2"])
+def test_404_warning_is_concise(
+    source: EcmwfOpenDataSource,
+    suffix: str,
+    missing_object_server: str,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    path = f"20261007000000-360h-enfo-ef.{suffix}"
+    url = f"{missing_object_server}/{path}"
+    store = HTTPStore(missing_object_server, client_options={"allow_http": True})
+    alternate: EcmwfOpenDataSource = "s3" if source == "gcs" else "gcs"
+
+    def download_one(current: EcmwfOpenDataSource) -> Path:
+        if current == source:
+            if suffix == "index":
+                obstore.get(store, path)
+            else:
+                obstore.get_ranges(store, path, starts=[0], ends=[10])
+        return Path("downloaded.grib2")
+
+    download = Mock(side_effect=download_one)
+
+    result = ecmwf_download_with_fallback((source, alternate), download)
+
+    assert result == Path("downloaded.grib2")
+    assert download.call_args_list == [call(source), call(alternate)]
+    assert [record.getMessage() for record in caplog.records] == [
+        (
+            f"ECMWF download from {source!r} failed, will fall back:"
+            f" FileNotFoundError: 404 Not Found for {url}"
+        )
+    ]
+    assert caplog.records[0].levelname == "WARNING"
+
+
+@pytest.mark.parametrize(
+    "error",
+    [
+        PermissionDeniedError(
+            _http_error_detail("https://example.com", "403 Forbidden")
+        ),
+        GenericError(
+            _http_error_detail("https://example.com", "503 Service Unavailable")
+        ),
+        GenericError(
+            _http_error_detail("https://example.com", "416 Range Not Satisfiable")
+        ),
+        FileNotFoundError("local file missing\nfull detail"),
+        FileNotFoundError(_http_error_detail("https://example.com", "403 Forbidden")),
+    ],
+)
+def test_other_warnings_keep_full_detail(
+    error: Exception, caplog: pytest.LogCaptureFixture
+) -> None:
+    download = Mock(side_effect=[error, Path("downloaded.grib2")])
+
+    assert ecmwf_download_with_fallback(("gcs", "s3"), download) == Path(
+        "downloaded.grib2"
+    )
+
+    assert [record.getMessage() for record in caplog.records] == [
+        f"ECMWF download from 'gcs' failed, will fall back: {error}"
+    ]
+
+
+@pytest.mark.parametrize("exception_type", [FileNotFoundError, GenericError])
+@pytest.mark.parametrize("url", ["https://example.com/forecast.index", None])
+def test_404_substring_shortens_unfamiliar_formats(
+    exception_type: type[Exception],
+    url: str | None,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    error = exception_type(f"404 Not Found: {url or 'missing object'}\nfull detail")
+    download = Mock(side_effect=[error, Path("downloaded.grib2")])
+
+    ecmwf_download_with_fallback(("gcs", "s3"), download)
+
+    detail = f"{exception_type.__name__}: 404 Not Found"
+    if url:
+        detail += f" for {url}"
+    assert [record.getMessage() for record in caplog.records] == [
+        f"ECMWF download from 'gcs' failed, will fall back: {detail}"
+    ]
+
+
+def test_exhausted_sources_raise_original_final_exception(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    errors = [
+        FileNotFoundError(
+            _http_error_detail(f"https://{source}.example.com/forecast.index")
+        )
+        for source in ("gcs", "s3")
+    ]
+    original_details = [str(error) for error in errors]
+    download = Mock(side_effect=errors)
+
+    with pytest.raises(FileNotFoundError) as caught:
+        ecmwf_download_with_fallback(("gcs", "s3"), download)
+
+    assert caught.value is errors[-1]
+    assert [str(error) for error in errors] == original_details
+    assert download.call_args_list == [call("gcs"), call("s3")]
+    assert len(caplog.records) == 2
+    assert all(record.levelname == "WARNING" for record in caplog.records)
+
+
+def test_success_does_not_warn_or_try_another_source(
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    download = Mock(return_value=Path("downloaded.grib2"))
+
+    assert ecmwf_download_with_fallback(("gcs", "s3"), download) == Path(
+        "downloaded.grib2"
+    )
+
+    download.assert_called_once_with("gcs")
+    assert not caplog.records