diff --git a/esphome/components/climate/climate.cpp b/esphome/components/climate/climate.cpp
index 51d91469c17..19a71959aac 100644
--- a/esphome/components/climate/climate.cpp
+++ b/esphome/components/climate/climate.cpp
@@ -485,10 +485,10 @@ void Climate::publish_state() {
 ClimateTraits Climate::get_traits() {
   auto traits = this->traits();
   // Wire custom mode pointers from Climate-owned storage
-  if (!this->supported_custom_fan_modes_.empty())
-    traits.set_supported_custom_fan_modes(&this->supported_custom_fan_modes_);
-  if (!this->supported_custom_presets_.empty())
-    traits.set_supported_custom_presets(&this->supported_custom_presets_);
+  if (this->supported_custom_fan_modes_)
+    traits.set_supported_custom_fan_modes(this->supported_custom_fan_modes_);
+  if (this->supported_custom_presets_)
+    traits.set_supported_custom_presets(this->supported_custom_presets_);
 #ifdef USE_CLIMATE_VISUAL_OVERRIDES
   if (!std::isnan(this->visual_min_temperature_override_)) {
     traits.set_visual_min_temperature(this->visual_min_temperature_override_);
@@ -706,7 +706,8 @@ const char *Climate::find_custom_fan_mode_(const char *custom_fan_mode) {
 }
 
 const char *Climate::find_custom_fan_mode_(const char *custom_fan_mode, size_t len) {
-  return vector_find(this->supported_custom_fan_modes_, custom_fan_mode, len);
+  return this->supported_custom_fan_modes_ ? vector_find(*this->supported_custom_fan_modes_, custom_fan_mode, len)
+                                           : nullptr;
 }
 
 const char *Climate::find_custom_preset_(const char *custom_preset) {
@@ -714,7 +715,7 @@ const char *Climate::find_custom_preset_(const char *custom_preset) {
 }
 
 const char *Climate::find_custom_preset_(const char *custom_preset, size_t len) {
-  return vector_find(this->supported_custom_presets_, custom_preset, len);
+  return this->supported_custom_presets_ ? vector_find(*this->supported_custom_presets_, custom_preset, len) : nullptr;
 }
 
 void Climate::dump_traits_(const char *tag) {
diff --git a/esphome/components/climate/climate.h b/esphome/components/climate/climate.h
index 6214afcbe32..69ea192456e 100644
--- a/esphome/components/climate/climate.h
+++ b/esphome/components/climate/climate.h
@@ -236,24 +236,37 @@ class Climate : public EntityBase {
 
   /// Set the supported custom fan modes (stored on Climate, referenced by ClimateTraits).
   void set_supported_custom_fan_modes(std::initializer_list<const char *> modes) {
-    this->supported_custom_fan_modes_ = modes;
+    if (!this->supported_custom_fan_modes_)
+      this->supported_custom_fan_modes_ =
+          new std::vector<const char *>();  // NOLINT - intentional leak, entity lives forever
+    *this->supported_custom_fan_modes_ = modes;
   }
   void set_supported_custom_fan_modes(const std::vector<const char *> &modes) {
-    this->supported_custom_fan_modes_ = modes;
+    if (!this->supported_custom_fan_modes_)
+      this->supported_custom_fan_modes_ = new std::vector<const char *>();  // NOLINT
+    *this->supported_custom_fan_modes_ = modes;
   }
   template<size_t N> void set_supported_custom_fan_modes(const char *const (&modes)[N]) {
-    this->supported_custom_fan_modes_.assign(modes, modes + N);
+    if (!this->supported_custom_fan_modes_)
+      this->supported_custom_fan_modes_ = new std::vector<const char *>();  // NOLINT
+    this->supported_custom_fan_modes_->assign(modes, modes + N);
   }
 
   /// Set the supported custom presets (stored on Climate, referenced by ClimateTraits).
   void set_supported_custom_presets(std::initializer_list<const char *> presets) {
-    this->supported_custom_presets_ = presets;
+    if (!this->supported_custom_presets_)
+      this->supported_custom_presets_ = new std::vector<const char *>();  // NOLINT
+    *this->supported_custom_presets_ = presets;
   }
   void set_supported_custom_presets(const std::vector<const char *> &presets) {
-    this->supported_custom_presets_ = presets;
+    if (!this->supported_custom_presets_)
+      this->supported_custom_presets_ = new std::vector<const char *>();  // NOLINT
+    *this->supported_custom_presets_ = presets;
   }
   template<size_t N> void set_supported_custom_presets(const char *const (&presets)[N]) {
-    this->supported_custom_presets_.assign(presets, presets + N);
+    if (!this->supported_custom_presets_)
+      this->supported_custom_presets_ = new std::vector<const char *>();  // NOLINT
+    this->supported_custom_presets_->assign(presets, presets + N);
   }
 
   /// Check if a custom fan mode is currently active.
@@ -366,11 +379,11 @@ class Climate : public EntityBase {
   LazyCallbackManager<void(ClimateCall &)> control_callback_{};
   ESPPreferenceObject rtc_;
 
-  /** Custom mode storage - owned by Climate, referenced by ClimateTraits via pointer.
+  /** Custom mode storage — allocated on first use, never freed (entity lives forever).
    * Pointers in these vectors must point to string literals or static data.
    */
-  std::vector<const char *> supported_custom_fan_modes_;
-  std::vector<const char *> supported_custom_presets_;
+  std::vector<const char *> *supported_custom_fan_modes_{nullptr};
+  std::vector<const char *> *supported_custom_presets_{nullptr};
 
 #ifdef USE_CLIMATE_VISUAL_OVERRIDES
   float visual_min_temperature_override_{NAN};