diff --git a/lib/microwaveprop_web/live/weather_map_live.ex b/lib/microwaveprop_web/live/weather_map_live.ex
index a044fa5e..a2f2cf3f 100644
--- a/lib/microwaveprop_web/live/weather_map_live.ex
+++ b/lib/microwaveprop_web/live/weather_map_live.ex
@@ -173,27 +173,22 @@ defmodule MicrowavepropWeb.WeatherMapLive do
     # the underlying cache can advance to while the worker is walking
     # f00→f18).
     #
-    # Hot-path mount: when the closest-to-now time happens to be the
-    # cached latest, use `latest_weather_grid/1` so mount stays under
-    # the LV socket join timeout (~10s). A ProfilesFile read for any
-    # other hour is a single ~2 MB ETF decode, also fine for mount.
+    # Mount stays cheap — no grid materialisation. The dead render
+    # would otherwise spend ~5–10 s materialising 92k cells through
+    # `WeatherLayers.derive`, blocking the HTTP response and tripping
+    # the LiveView socket join timeout. The JS hook fires `map_bounds`
+    # via `requestAnimationFrame` immediately after mount, and the
+    # existing `handle_event("map_bounds", ...)` path drives the
+    # initial layer paint via `update_weather`.
     valid_times = Weather.available_weather_valid_times()
-    latest_vt = Weather.latest_grid_valid_time()
     initial_vt = pick_initial_valid_time(valid_times)
 
-    data =
-      cond do
-        is_nil(initial_vt) -> []
-        initial_vt == latest_vt -> Weather.latest_weather_grid(@initial_bounds)
-        true -> Weather.weather_grid_at(initial_vt, @initial_bounds)
-      end
-
     {:ok,
      assign(socket,
        page_title: "Weather Map",
        layers: @layers,
        selected_layer: "temperature",
-       initial_data_json: Jason.encode!(data),
+       initial_data_json: "[]",
        valid_time: initial_vt,
        valid_times: valid_times,
        initial_valid_times_json: Jason.encode!(Enum.map(valid_times, &DateTime.to_iso8601/1)),