diff --git a/web/world/js/tests/weather.selftest.js b/web/world/js/tests/weather.selftest.js
index b4bd053..5b5da0e 100644
--- a/web/world/js/tests/weather.selftest.js
+++ b/web/world/js/tests/weather.selftest.js
@@ -11,7 +11,7 @@
 // call it with the fetched storm defs.
 
 import {
-  createWindField, validateStorm, gustEnvelope, GUST, RAIN_TIME_COMPRESSION,
+  createWindField, validateStorm, validateSiteWind, gustEnvelope, GUST, RAIN_TIME_COMPRESSION,
   stormStats, forecastFor, hailBlockFor,
 } from '../weather.core.js';
 
@@ -324,6 +324,24 @@ export function weatherCases(storms) {
     assert(maxRatio > 1.3, `funnel didn't strengthen the downdraft (max ${maxRatio.toFixed(2)}×) — it should ride local speed`);
   });
 
+  test('validateSiteWind: a good funnel passes, a bad one fails loud', () => {
+    const ok = validateSiteWind({ venturi: [{ x: -6, z: 4, axis: -1.08, gain: 1.4, radius: 5, sharp: 3 }] }, 's');
+    assert(ok.ok, `a valid venturi was rejected: ${ok.errors.join('; ')}`);
+    assert(validateSiteWind(null, 's').ok, 'a site with no wind block should validate');
+    assert(validateSiteWind({}, 's').ok, 'an empty wind block should validate');
+    assert(validateSiteWind({ venturi: [] }, 's').ok, 'an empty venturi list should validate');
+    for (const [label, bad] of [
+      ['gain < 1 (a venturi speeds up, never slows)', { venturi: [{ x: 0, z: 0, gain: 0.7 }] }],
+      ['gain absurd', { venturi: [{ x: 0, z: 0, gain: 9 }] }],
+      ['no x,z', { venturi: [{ axis: 1, gain: 1.4 }] }],
+      ['axis not finite', { venturi: [{ x: 0, z: 0, axis: 'south' }] }],
+      ['radius <= 0', { venturi: [{ x: 0, z: 0, radius: 0 }] }],
+      ['venturi not an array', { venturi: { x: 0 } }],
+    ]) {
+      assert(!validateSiteWind(bad, 's').ok, `validateSiteWind accepted a bad funnel: ${label}`);
+    }
+  });
+
   test('an empty venturi list is a perfect no-op (backyard_01 is untouched)', () => {
     const def = storms.storm_02_wildnight;
     const bare = createWindField(def);
diff --git a/web/world/js/weather.core.js b/web/world/js/weather.core.js
index 1b2e478..b21cd0a 100644
--- a/web/world/js/weather.core.js
+++ b/web/world/js/weather.core.js
@@ -807,3 +807,29 @@ export function validateStorm(def, name = 'storm') {
 
   return { ok: errors.length === 0, errors };
 }
+
+// ---------- site wind validator (SPRINT10 site-as-data) ----------
+// A site's `wind` block is hand-authored data like a storm, so it fails loud
+// the same way. Lane A calls this at site load; setVenturi clamps defensively
+// too, but a clamp hides a typo and this names it. Wind personality that lives
+// in site JSON: venturi funnels (and later, per-site shelter overrides).
+export function validateSiteWind(wind, name = 'site') {
+  const errors = [];
+  const bad = (m) => errors.push(`${name}.wind: ${m}`);
+  if (wind == null) return { ok: true, errors };          // a site with no wind block is fine
+  if (typeof wind !== 'object') { bad('must be an object'); return { ok: false, errors }; }
+
+  if (wind.venturi != null) {
+    if (!Array.isArray(wind.venturi)) bad('venturi must be an array of funnel zones');
+    else wind.venturi.forEach((v, i) => {
+      const at = `venturi[${i}]`;
+      if (!Number.isFinite(v.x) || !Number.isFinite(v.z)) bad(`${at} needs finite x,z (the throat centre)`);
+      if (v.axis != null && !Number.isFinite(v.axis)) bad(`${at}.axis must be radians (the direction the gap runs)`);
+      if (v.gain != null && !(v.gain >= 1)) bad(`${at}.gain must be >= 1 — a venturi speeds wind UP; use shelters to slow it (got ${v.gain})`);
+      if (v.gain != null && v.gain > 3) bad(`${at}.gain ${v.gain} is a wind tunnel, not a gap — cap ~2`);
+      if (v.radius != null && !(v.radius > 0)) bad(`${at}.radius must be > 0 metres`);
+      if (v.sharp != null && !(v.sharp >= 1)) bad(`${at}.sharp must be >= 1 (alignment falloff exponent)`);
+    });
+  }
+  return { ok: errors.length === 0, errors };
+}
diff --git a/web/world/js/weather.js b/web/world/js/weather.js
index b49b92d..5b70807 100644
--- a/web/world/js/weather.js
+++ b/web/world/js/weather.js
@@ -11,11 +11,14 @@
 
 import * as THREE from '../vendor/three.module.js';
 import {
-  createWindField, validateStorm, GUST, RAIN_TIME_COMPRESSION,
+  createWindField, validateStorm, validateSiteWind, GUST, RAIN_TIME_COMPRESSION,
   hailBlockFor, stormStats, forecastFor,
 } from './weather.core.js';
 
-export { GUST, validateStorm, RAIN_TIME_COMPRESSION, hailBlockFor, stormStats, forecastFor };
+export {
+  GUST, validateStorm, validateSiteWind, RAIN_TIME_COMPRESSION,
+  hailBlockFor, stormStats, forecastFor,
+};
 
 const kmh = (ms) => ms * 3.6;
 const band = (b, fmt) => (b.hi - b.lo < 0.05 ? fmt(b.lo) : `${fmt(b.lo)}–${fmt(b.hi)}`);