diff --git a/backend/migrations/Version20260403000000.php b/backend/migrations/Version20260403000000.php
new file mode 100644
index 0000000..75fb7f6
--- /dev/null
+++ b/backend/migrations/Version20260403000000.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+final class Version20260403000000 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Ajout eta_hours sur impact_score — horizon prévu d\'impact côtier';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE impact_score ADD COLUMN eta_hours INT DEFAULT NULL');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE impact_score DROP COLUMN IF EXISTS eta_hours');
+    }
+}
diff --git a/backend/src/Controller/SpotScoreController.php b/backend/src/Controller/SpotScoreController.php
index 3e7c16c..110c0c3 100644
--- a/backend/src/Controller/SpotScoreController.php
+++ b/backend/src/Controller/SpotScoreController.php
@@ -64,13 +64,13 @@ class SpotScoreController extends AbstractController
     /**
      * Score à un instant précis (sans cache).
      *
-     * @return array{value: int, level: string, distance: float|null, density: float|null, trend: string|null, computedAt: string}|null
+     * @return array{value: int, level: string, distance: float|null, density: float|null, trend: string|null, etaHours: int|null, computedAt: string}|null
      */
     private function loadScoreAt(string $spotId, \DateTimeImmutable $at): ?array
     {
         $row = $this->connection->fetchAssociative(
             'SELECT score, level, distance_to_nearest_sargassum AS distance,
-                    density_estimate AS density, trend, timestamp AS computed_at
+                    density_estimate AS density, trend, eta_hours, timestamp AS computed_at
              FROM impact_score
              WHERE coastal_point_id = :spotId AND timestamp <= :at
              ORDER BY timestamp DESC LIMIT 1',
@@ -131,16 +131,17 @@ class SpotScoreController extends AbstractController
 
     /**
      * @param array<string, mixed> $row
-     * @return array{value: int, level: string, distance: float|null, density: float|null, trend: string|null, computedAt: string}
+     * @return array{value: int, level: string, distance: float|null, density: float|null, trend: string|null, etaHours: int|null, computedAt: string}
      */
     private function formatScore(array $row): array
     {
         return [
             'value'      => (int) $row['score'],
             'level'      => $row['level'],
-            'distance'   => $row['distance'] !== null ? (float) $row['distance'] : null,
-            'density'    => $row['density']  !== null ? (float) $row['density']  : null,
+            'distance'   => $row['distance']  !== null ? (float) $row['distance']  : null,
+            'density'    => $row['density']   !== null ? (float) $row['density']   : null,
             'trend'      => $row['trend'],
+            'etaHours'   => $row['eta_hours'] !== null ? (int) $row['eta_hours']   : null,
             'computedAt' => $row['computed_at'],
         ];
     }
diff --git a/backend/src/Entity/ImpactScore.php b/backend/src/Entity/ImpactScore.php
index 42dbe75..cfca589 100644
--- a/backend/src/Entity/ImpactScore.php
+++ b/backend/src/Entity/ImpactScore.php
@@ -49,6 +49,13 @@ class ImpactScore
     #[ORM\Column(length: 20, nullable: true)]
     private ?string $trend = null;
 
+    /**
+     * Horizon (en heures) auquel les sargasses devraient atteindre le spot.
+     * 0 = impact en cours, null = aucun impact prévu dans les 48h.
+     */
+    #[ORM\Column(nullable: true)]
+    private ?int $etaHours = null;
+
     public function __construct()
     {
         $this->timestamp = new \DateTimeImmutable();
@@ -71,4 +78,6 @@ class ImpactScore
     public function setDensityEstimate(?float $d): static { $this->densityEstimate = $d; return $this; }
     public function getTrend(): ?string { return $this->trend; }
     public function setTrend(?string $trend): static { $this->trend = $trend; return $this; }
+    public function getEtaHours(): ?int { return $this->etaHours; }
+    public function setEtaHours(?int $etaHours): static { $this->etaHours = $etaHours; return $this; }
 }
diff --git a/backend/src/Service/Forecast/ImpactScoreService.php b/backend/src/Service/Forecast/ImpactScoreService.php
index cd4486d..c23de81 100644
--- a/backend/src/Service/Forecast/ImpactScoreService.php
+++ b/backend/src/Service/Forecast/ImpactScoreService.php
@@ -31,6 +31,7 @@ class ImpactScoreService
     private const MAX_DENSITY_KM2 = 100;   // 100 km² = densité maximale
     private const MAX_APPROACH_KMH = 5;    // 5 km/h = vitesse d'approche max
     private const CACHE_TTL = 10_800;      // 3h
+    private const ETA_BUFFER_M = 5_000;    // 5 km : seuil "impact imminent" sur le spot
 
     // Bonus feedback : +8 pts si présence confirmée dans les 6h et dans rayon 20km
     private const FEEDBACK_RADIUS_M  = 20_000;
@@ -61,14 +62,13 @@ class ImpactScoreService
             return;
         }
 
-        $obsId      = (string) $observation->getId();
-        $forecastH6 = $this->findForecastByHorizon($forecasts, 6);
+        $obsId = (string) $observation->getId();
 
         foreach ($spots as $spot) {
             $spotId = (string) $spot->getId();
 
             try {
-                $score = $this->computeScore($spot, $obsId, $forecastH6);
+                $score = $this->computeScore($spot, $obsId, $forecasts);
                 $this->persistScore($spot, $score);
                 $this->invalidateCache($spotId);
 
@@ -90,7 +90,7 @@ class ImpactScoreService
     /**
      * Retourne le score mis en cache pour un spot (TTL 3h).
      *
-     * @return array{value: int, level: string, distance: float|null, density: float|null, trend: string|null, computedAt: string}|null
+     * @return array{value: int, level: string, distance: float|null, density: float|null, trend: string|null, etaHours: int|null, computedAt: string}|null
      */
     public function getCachedScore(string $spotId): ?array
     {
@@ -104,8 +104,11 @@ class ImpactScoreService
 
     // -------------------------------------------------------------------------
 
-    /** @return array{score: int, level: string, distance: float|null, density: float, trend: string} */
-    private function computeScore(CoastalPoint $spot, string $obsId, ?SargassumForecast $forecastH6): array
+    /**
+     * @param array<int, SargassumForecast> $forecasts
+     * @return array{score: int, level: string, distance: float|null, density: float, trend: string, etaHours: int|null}
+     */
+    private function computeScore(CoastalPoint $spot, string $obsId, array $forecasts): array
     {
         $spotId = (string) $spot->getId();
 
@@ -117,6 +120,7 @@ class ImpactScoreService
         }
 
         $coverageKm2 = $this->getCoverageArea($obsId);
+        $forecastH6  = $this->findForecastByHorizon($forecasts, 6);
 
         // Vitesse d'approche : delta distance entre now et H+6 (km/h)
         $approachKmh = 0.0;
@@ -130,17 +134,20 @@ class ImpactScoreService
         // Tendance
         $previousDistance = $this->getPreviousDistance($spotId);
         $trend = match (true) {
-            $previousDistance === null        => 'stable',
+            $previousDistance === null           => 'stable',
             $distanceM < $previousDistance * 0.9 => 'increasing',
             $distanceM > $previousDistance * 1.1 => 'decreasing',
-            default                           => 'stable',
+            default                              => 'stable',
         };
 
+        // ETA côtier
+        $etaHours = $this->computeEta($spotId, $distanceM, $forecasts);
+
         // Calcul des composantes
-        $distanceScore  = max(0.0, 1.0 - $distanceM / self::MAX_DISTANCE_M) * 40;
-        $densityScore   = min($coverageKm2 / self::MAX_DENSITY_KM2, 1.0) * 30;
-        $velocityScore  = min(max($approachKmh, 0.0) / self::MAX_APPROACH_KMH, 1.0) * 20;
-        $trendScore     = match ($trend) { 'increasing' => 10, 'stable' => 5, default => 0 };
+        $distanceScore = max(0.0, 1.0 - $distanceM / self::MAX_DISTANCE_M) * 40;
+        $densityScore  = min($coverageKm2 / self::MAX_DENSITY_KM2, 1.0) * 30;
+        $velocityScore = min(max($approachKmh, 0.0) / self::MAX_APPROACH_KMH, 1.0) * 20;
+        $trendScore    = match ($trend) { 'increasing' => 10, 'stable' => 5, default => 0 };
 
         // Bonus feedback terrain récent
         $feedbackBonus = $this->getFeedbackBonus($spotId);
@@ -154,9 +161,37 @@ class ImpactScoreService
             'distance' => round($distanceM / 1000, 2),
             'density'  => round($coverageKm2, 2),
             'trend'    => $trend,
+            'etaHours' => $etaHours,
         ];
     }
 
+    /**
+     * Calcule l'horizon (en h) auquel les sargasses devraient atteindre le spot.
+     * Retourne 0 si impact déjà en cours, null si aucun impact prévu dans 48h.
+     *
+     * @param array<int, SargassumForecast> $forecasts
+     */
+    private function computeEta(string $spotId, float $currentDistanceM, array $forecasts): ?int
+    {
+        if ($currentDistanceM < self::ETA_BUFFER_M) {
+            return 0; // impact en cours
+        }
+
+        foreach ([6, 12, 24, 48] as $horizon) {
+            $forecast = $this->findForecastByHorizon($forecasts, $horizon);
+            if ($forecast === null) {
+                continue;
+            }
+
+            $distM = $this->getDistanceToNearestForecast($spotId, (string) $forecast->getId());
+            if ($distM !== null && $distM < self::ETA_BUFFER_M) {
+                return $horizon;
+            }
+        }
+
+        return null;
+    }
+
     private function getDistanceToNearestSargassum(string $spotId, string $obsId): ?float
     {
         $row = $this->connection->fetchAssociative(
@@ -221,7 +256,7 @@ class ImpactScoreService
             : null;
     }
 
-    /** @param array{score: int, level: string, distance: float|null, density: float, trend: string} $data */
+    /** @param array{score: int, level: string, distance: float|null, density: float, trend: string, etaHours: int|null} $data */
     private function persistScore(CoastalPoint $spot, array $data): void
     {
         $s = new ImpactScore();
@@ -231,16 +266,17 @@ class ImpactScoreService
         $s->setDistanceToNearestSargassum($data['distance']);
         $s->setDensityEstimate($data['density']);
         $s->setTrend($data['trend']);
+        $s->setEtaHours($data['etaHours']);
 
         $this->em->persist($s);
     }
 
-    /** @return array{value: int, level: string, distance: float|null, density: float|null, trend: string|null, computedAt: string}|null */
+    /** @return array{value: int, level: string, distance: float|null, density: float|null, trend: string|null, etaHours: int|null, computedAt: string}|null */
     private function loadLatestScore(string $spotId): ?array
     {
         $row = $this->connection->fetchAssociative(
             'SELECT score, level, distance_to_nearest_sargassum AS distance,
-                    density_estimate AS density, trend, timestamp AS computed_at
+                    density_estimate AS density, trend, eta_hours, timestamp AS computed_at
              FROM impact_score
              WHERE coastal_point_id = :spotId
              ORDER BY timestamp DESC LIMIT 1',
@@ -254,9 +290,10 @@ class ImpactScoreService
         return [
             'value'      => (int) $row['score'],
             'level'      => $row['level'],
-            'distance'   => $row['distance'] !== null ? (float) $row['distance'] : null,
-            'density'    => $row['density']  !== null ? (float) $row['density']  : null,
+            'distance'   => $row['distance']  !== null ? (float) $row['distance']  : null,
+            'density'    => $row['density']   !== null ? (float) $row['density']   : null,
             'trend'      => $row['trend'],
+            'etaHours'   => $row['eta_hours'] !== null ? (int) $row['eta_hours']   : null,
             'computedAt' => $row['computed_at'],
         ];
     }
@@ -280,10 +317,10 @@ class ImpactScoreService
         };
     }
 
-    /** @return array{score: int, level: string, distance: null, density: float, trend: string} */
+    /** @return array{score: int, level: string, distance: null, density: float, trend: string, etaHours: null} */
     private function emptyScore(): array
     {
-        return ['score' => 0, 'level' => 'low', 'distance' => null, 'density' => 0.0, 'trend' => 'stable'];
+        return ['score' => 0, 'level' => 'low', 'distance' => null, 'density' => 0.0, 'trend' => 'stable', 'etaHours' => null];
     }
 
     private function getFeedbackBonus(string $spotId): float
diff --git a/frontend/src/components/SpotPanel/SpotPanel.css b/frontend/src/components/SpotPanel/SpotPanel.css
index 0e7f754..5e9c467 100644
--- a/frontend/src/components/SpotPanel/SpotPanel.css
+++ b/frontend/src/components/SpotPanel/SpotPanel.css
@@ -124,6 +124,27 @@
 .gauge--medium .spot-panel__gauge-fill { background: #eab308; }
 .gauge--high .spot-panel__gauge-fill   { background: #ef4444; }
 
+/* ETA */
+.spot-panel__eta {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  padding: 11px 16px;
+  border-radius: 14px;
+  border: 2px solid rgba(0,0,0,0.15);
+  margin-bottom: 10px;
+  font-weight: 700;
+  font-size: 15px;
+  font-family: 'Fredoka One', cursive;
+}
+.eta--now   { background: #fee2e2; color: #b91c1c; border-color: #fca5a5; }
+.eta--soon  { background: #fef9c3; color: #92400e; border-color: #fde68a; }
+.eta--later { background: #fff7ed; color: #9a3412; border-color: #fed7aa; }
+.eta--safe  { background: #dcfce7; color: #15803d; border-color: #86efac; }
+
+.spot-panel__eta-icon  { font-size: 20px; line-height: 1; flex-shrink: 0; }
+.spot-panel__eta-label { font-family: 'Fredoka', sans-serif; font-weight: 600; }
+
 /* Trend */
 .spot-panel__trend {
   display: flex;
diff --git a/frontend/src/components/SpotPanel/SpotPanel.jsx b/frontend/src/components/SpotPanel/SpotPanel.jsx
index 809a2b1..b4206a0 100644
--- a/frontend/src/components/SpotPanel/SpotPanel.jsx
+++ b/frontend/src/components/SpotPanel/SpotPanel.jsx
@@ -12,6 +12,15 @@ const TREND_CONFIG = {
   decreasing: { icon: '📉', label: 'Amélioration en cours',    cls: 'trend--good' },
 };
 
+function etaLabel(etaHours) {
+  if (etaHours === 0)  return { icon: '🚨', label: 'Impact en cours',           cls: 'eta--now'  };
+  if (etaHours === 6)  return { icon: '⚠️',  label: 'Impact prévu dans ~6h',     cls: 'eta--soon' };
+  if (etaHours === 12) return { icon: '⚠️',  label: 'Impact prévu dans ~12h',    cls: 'eta--soon' };
+  if (etaHours === 24) return { icon: '🕐',  label: 'Impact prévu dans ~24h',    cls: 'eta--later' };
+  if (etaHours === 48) return { icon: '🕐',  label: 'Impact prévu dans ~48h',    cls: 'eta--later' };
+  return                       { icon: '✅',  label: 'Aucun impact prévu (48h)',  cls: 'eta--safe' };
+}
+
 const HORIZON_LABELS = { now: 'Maintenant', h6: '+6h', h12: '+12h', h24: '+24h', h48: '+48h' };
 
 export default function SpotPanel({ spot, activeStep, onClose }) {
@@ -72,6 +81,16 @@ export default function SpotPanel({ spot, activeStep, onClose }) {
             ? <p className="spot-panel__no-data">Aucune donnée pour cet horizon.</p>
             : (
               <>
+                {activeStep === 'now' && (() => {
+                  const eta = etaLabel(displayScore.etaHours ?? undefined);
+                  return (
+                    <div className={`spot-panel__eta ${eta.cls}`}>
+                      <span className="spot-panel__eta-icon">{eta.icon}</span>
+                      <span className="spot-panel__eta-label">{eta.label}</span>
+                    </div>
+                  );
+                })()}
+
                 <div className={`spot-panel__gauge gauge--${lvl}`}>
                   <div className="spot-panel__gauge-top">
                     <span className="spot-panel__gauge-label">{LEVEL_LABEL[lvl] ?? lvl}</span>