diff --git a/CHANGELOG.md b/CHANGELOG.md
index bee7e547e..ca48b665d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ All notable changes to this project will be documented in this file.
 - HASPmota more attributes (#20744)
 - QMC5883l check for overflow and scale reading (#20643)
 - TasMesh support for LWT messages (#20392)
+- Show calculated heat index if temperature and humidity is available with ``#define USE_HEAT_INDEX`` (#4771)
 
 ### Breaking Changed
 
diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index ee1f6b76c..ddd9bb3b3 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -118,6 +118,7 @@ The latter links can be used for OTA upgrades too like ``OtaUrl https://ota.tasm
 
 ## Changelog v13.4.0.1
 ### Added
+- Show calculated heat index if temperature and humidity is available with ``#define USE_HEAT_INDEX`` [#4771](https://github.com/arendst/Tasmota/issues/4771)
 - TasMesh support for LWT messages [#20392](https://github.com/arendst/Tasmota/issues/20392)
 - QMC5883l check for overflow and scale reading [#20643](https://github.com/arendst/Tasmota/issues/20643)
 - HASPmota `p<x>b<y>.delete` to delete an object [#20735](https://github.com/arendst/Tasmota/issues/20735)
diff --git a/tasmota/include/i18n.h b/tasmota/include/i18n.h
index 1437473fa..2f57cde82 100644
--- a/tasmota/include/i18n.h
+++ b/tasmota/include/i18n.h
@@ -95,6 +95,7 @@
 #define D_JSON_HALLEFFECT "HallEffect"
 #define D_JSON_HALTING "Halting"
 #define D_JSON_HEAPSIZE "Heap"
+#define D_JSON_HEATINDEX "HeatIndex"
 #define D_JSON_HIGH "High"
 #define D_JSON_HOST_NOT_FOUND "Host not found"
 #define D_JSON_FILE_NOT_FOUND "File not found"
@@ -948,6 +949,7 @@ const char HTTP_SNS_F_ABS_HUM[]     PROGMEM = "{s}%s "  D_ABSOLUTE_HUMIDITY   "{
 
 const char HTTP_SNS_HUM[]           PROGMEM = "{s}%s "  D_HUMIDITY            "{m}%s " D_UNIT_PERCENT             "{e}";
 const char HTTP_SNS_DEW[]           PROGMEM = "{s}%s "  D_DEWPOINT            "{m}%s " D_UNIT_DEGREE            "%c{e}";
+const char HTTP_SNS_HEATINDEX[]     PROGMEM = "{s}%s "  D_HEATINDEX           "{m}%s " D_UNIT_DEGREE            "%c{e}";
 const char HTTP_SNS_PRESSURE[]      PROGMEM = "{s}%s "  D_PRESSURE            "{m}%s "                          "%s{e}";
 const char HTTP_SNS_SEAPRESSURE[]   PROGMEM = "{s}%s "  D_PRESSUREATSEALEVEL  "{m}%s "                          "%s{e}";
 const char HTTP_SNS_ANALOG[]        PROGMEM = "{s}%s "  D_ANALOG_INPUT      "%d{m}%d"                             "{e}";
diff --git a/tasmota/language/af_AF.h b/tasmota/language/af_AF.h
index a0b81d637..51ce74bee 100644
--- a/tasmota/language/af_AF.h
+++ b/tasmota/language/af_AF.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Groep"
 #define D_HOST "Gasheer"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Gasheername"
 #define D_HUMIDITY "Humiditeit"
 #define D_ILLUMINANCE "Verligting"
diff --git a/tasmota/language/bg_BG.h b/tasmota/language/bg_BG.h
index eb460a30e..f7cf90215 100644
--- a/tasmota/language/bg_BG.h
+++ b/tasmota/language/bg_BG.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Група"
 #define D_HOST "Хост"
 #define D_HALL_EFFECT "Ефект на Хол"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Име на хоста"
 #define D_HUMIDITY "Влажност"
 #define D_ILLUMINANCE "Осветеност"
diff --git a/tasmota/language/ca_AD.h b/tasmota/language/ca_AD.h
index ab32cab34..c5663ff55 100644
--- a/tasmota/language/ca_AD.h
+++ b/tasmota/language/ca_AD.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Grup"
 #define D_HOST "Hoste"
 #define D_HALL_EFFECT "Efecte Hall"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Nom de màquina"
 #define D_HUMIDITY "Humitat"
 #define D_ILLUMINANCE "Iluminància"
diff --git a/tasmota/language/cs_CZ.h b/tasmota/language/cs_CZ.h
index 99b050e9d..29d2dbf72 100644
--- a/tasmota/language/cs_CZ.h
+++ b/tasmota/language/cs_CZ.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Skupina"
 #define D_HOST "Server"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Název serveru"
 #define D_HUMIDITY "Vlhkost"
 #define D_ILLUMINANCE "Osvětlení"
diff --git a/tasmota/language/de_DE.h b/tasmota/language/de_DE.h
index 44ea49961..45d9dc734 100644
--- a/tasmota/language/de_DE.h
+++ b/tasmota/language/de_DE.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Gruppe"
 #define D_HOST "Host"
 #define D_HALL_EFFECT "Hall Effekt"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Hostname"
 #define D_HUMIDITY "Feuchtigkeit"
 #define D_ILLUMINANCE "Beleuchtungsstärke"
diff --git a/tasmota/language/el_GR.h b/tasmota/language/el_GR.h
index 3355065af..7d6c8e1c3 100644
--- a/tasmota/language/el_GR.h
+++ b/tasmota/language/el_GR.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Ομάδα"
 #define D_HOST "Host"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Hostname"
 #define D_HUMIDITY "Υγρασία"
 #define D_ILLUMINANCE "Φωτεινότητα"
diff --git a/tasmota/language/en_GB.h b/tasmota/language/en_GB.h
index 6748ed35f..ccdae7d73 100644
--- a/tasmota/language/en_GB.h
+++ b/tasmota/language/en_GB.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Group"
 #define D_HOST "Host"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Hostname"
 #define D_HUMIDITY "Humidity"
 #define D_ILLUMINANCE "Illuminance"
diff --git a/tasmota/language/es_ES.h b/tasmota/language/es_ES.h
index e6582e91a..66b650bef 100644
--- a/tasmota/language/es_ES.h
+++ b/tasmota/language/es_ES.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Grupo"
 #define D_HOST "Host"
 #define D_HALL_EFFECT "Efecto Hall"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Hostname"
 #define D_HUMIDITY "Humedad"
 #define D_ILLUMINANCE "Luminancia"
diff --git a/tasmota/language/fr_FR.h b/tasmota/language/fr_FR.h
index 608e7fbaa..af20f1b83 100644
--- a/tasmota/language/fr_FR.h
+++ b/tasmota/language/fr_FR.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Groupe"
 #define D_HOST "Hôte"
 #define D_HALL_EFFECT "Effet Hall"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Nom d'Hôte"
 #define D_HUMIDITY "Humidité"
 #define D_ILLUMINANCE "Éclairement"
diff --git a/tasmota/language/fy_NL.h b/tasmota/language/fy_NL.h
index 86c47c27a..37f74edf7 100644
--- a/tasmota/language/fy_NL.h
+++ b/tasmota/language/fy_NL.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Groep"
 #define D_HOST "Host"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Hostnamme"
 #define D_HUMIDITY "Feuchte"
 #define D_ILLUMINANCE "Beljochting"
diff --git a/tasmota/language/he_HE.h b/tasmota/language/he_HE.h
index f0ae6001c..7f33543c5 100644
--- a/tasmota/language/he_HE.h
+++ b/tasmota/language/he_HE.h
@@ -119,6 +119,7 @@
 #define D_GROUP "קבוצה"
 #define D_HOST "מארח"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "שם מארח"
 #define D_HUMIDITY "לחות"
 #define D_ILLUMINANCE "רמת חשיפה"
diff --git a/tasmota/language/hu_HU.h b/tasmota/language/hu_HU.h
index 176dddc0b..f78c7e5f3 100644
--- a/tasmota/language/hu_HU.h
+++ b/tasmota/language/hu_HU.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Csoport"
 #define D_HOST "Hoszt"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Hosztnév"
 #define D_HUMIDITY "Páratartalom"
 #define D_ILLUMINANCE "Megvilágítás"
diff --git a/tasmota/language/it_IT.h b/tasmota/language/it_IT.h
index b5d948491..335e72349 100644
--- a/tasmota/language/it_IT.h
+++ b/tasmota/language/it_IT.h
@@ -119,6 +119,7 @@
 #define D_GROUP                "Gruppo"
 #define D_HOST                 "Host"
 #define D_HALL_EFFECT          "Effetto hall"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME             "Nome host"
 #define D_HUMIDITY             "Umidità"
 #define D_ILLUMINANCE          "Illuminazione"
diff --git a/tasmota/language/ko_KO.h b/tasmota/language/ko_KO.h
index c3248c9f5..598dc12a1 100644
--- a/tasmota/language/ko_KO.h
+++ b/tasmota/language/ko_KO.h
@@ -119,6 +119,7 @@
 #define D_GROUP "그룹"
 #define D_HOST "호스트"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "호스트이름"
 #define D_HUMIDITY "습도"
 #define D_ILLUMINANCE "조도"
diff --git a/tasmota/language/nl_NL.h b/tasmota/language/nl_NL.h
index 48ff12599..a0aec757c 100644
--- a/tasmota/language/nl_NL.h
+++ b/tasmota/language/nl_NL.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Groep"
 #define D_HOST "Host"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Hostnaam"
 #define D_HUMIDITY "Luchtvochtigheid"
 #define D_ILLUMINANCE "Verlichtingssterkte"
diff --git a/tasmota/language/pl_PL.h b/tasmota/language/pl_PL.h
index 12ce56032..5d96c6ce6 100644
--- a/tasmota/language/pl_PL.h
+++ b/tasmota/language/pl_PL.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Grupa"
 #define D_HOST "Serwer"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Nazwa serwera"
 #define D_HUMIDITY "Wilgotność"
 #define D_ILLUMINANCE "Podświetlanie"
diff --git a/tasmota/language/pt_BR.h b/tasmota/language/pt_BR.h
index e3d5e8694..133750f64 100644
--- a/tasmota/language/pt_BR.h
+++ b/tasmota/language/pt_BR.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Grupo"
 #define D_HOST "Host"
 #define D_HALL_EFFECT "Efeito Hall"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Nome do Host"
 #define D_HUMIDITY "Umidade"
 #define D_ILLUMINANCE "Luminância"
diff --git a/tasmota/language/pt_PT.h b/tasmota/language/pt_PT.h
index f396d366f..564afed03 100644
--- a/tasmota/language/pt_PT.h
+++ b/tasmota/language/pt_PT.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Grupo"
 #define D_HOST "Anfitrião"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Nome Anfitrião"
 #define D_HUMIDITY "Humidade"
 #define D_ILLUMINANCE "Luminâcia"
diff --git a/tasmota/language/ro_RO.h b/tasmota/language/ro_RO.h
index 9d05f17b2..d379bc8bd 100644
--- a/tasmota/language/ro_RO.h
+++ b/tasmota/language/ro_RO.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Grup"
 #define D_HOST "Gazdă"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Hostname"
 #define D_HUMIDITY "Umiditate"
 #define D_ILLUMINANCE "Iluminare"
diff --git a/tasmota/language/ru_RU.h b/tasmota/language/ru_RU.h
index bc2598952..0cdb64b58 100644
--- a/tasmota/language/ru_RU.h
+++ b/tasmota/language/ru_RU.h
@@ -120,6 +120,7 @@
 #define D_GROUP "Группа"
 #define D_HOST "Хост"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Имя хоста"
 #define D_HUMIDITY "Влажность"
 #define D_ILLUMINANCE "Освещенность"
diff --git a/tasmota/language/sk_SK.h b/tasmota/language/sk_SK.h
index 256feff7e..d6bc76ac1 100644
--- a/tasmota/language/sk_SK.h
+++ b/tasmota/language/sk_SK.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Skupina"
 #define D_HOST "Server"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Názov servera"
 #define D_HUMIDITY "Vlhkosť"
 #define D_ILLUMINANCE "Osvetlenie"
diff --git a/tasmota/language/sv_SE.h b/tasmota/language/sv_SE.h
index 3c1445193..e0e6c0594 100644
--- a/tasmota/language/sv_SE.h
+++ b/tasmota/language/sv_SE.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Grupp"
 #define D_HOST "Värd"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Värdnamn"
 #define D_HUMIDITY "Fuktighet"
 #define D_ILLUMINANCE "Belysnings"
diff --git a/tasmota/language/tr_TR.h b/tasmota/language/tr_TR.h
index fd15dd5f4..35609c1c0 100644
--- a/tasmota/language/tr_TR.h
+++ b/tasmota/language/tr_TR.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Grup"
 #define D_HOST "Host"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Host Adresi"
 #define D_HUMIDITY "Nem"
 #define D_ILLUMINANCE "Aydınlık"
diff --git a/tasmota/language/uk_UA.h b/tasmota/language/uk_UA.h
index bda176a23..fcb3356c0 100644
--- a/tasmota/language/uk_UA.h
+++ b/tasmota/language/uk_UA.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Група"
 #define D_HOST "Хост"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Назва хосту"
 #define D_HUMIDITY "Вологість"
 #define D_ILLUMINANCE "Освітленність"
diff --git a/tasmota/language/vi_VN.h b/tasmota/language/vi_VN.h
index 27924e49d..097383ce0 100644
--- a/tasmota/language/vi_VN.h
+++ b/tasmota/language/vi_VN.h
@@ -119,6 +119,7 @@
 #define D_GROUP "Nhóm"
 #define D_HOST "Máy chủ"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "Tên máy chủ"
 #define D_HUMIDITY "Độ ẩm"
 #define D_ILLUMINANCE "Độ sáng"
diff --git a/tasmota/language/zh_CN.h b/tasmota/language/zh_CN.h
index 5064d894c..004fa4b47 100644
--- a/tasmota/language/zh_CN.h
+++ b/tasmota/language/zh_CN.h
@@ -119,6 +119,7 @@
 #define D_GROUP "组:"
 #define D_HOST "主机"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "主机名"
 #define D_HUMIDITY "湿度"
 #define D_ILLUMINANCE "照度"
diff --git a/tasmota/language/zh_TW.h b/tasmota/language/zh_TW.h
index 4137357a1..1487bc0f2 100644
--- a/tasmota/language/zh_TW.h
+++ b/tasmota/language/zh_TW.h
@@ -119,6 +119,7 @@
 #define D_GROUP "群組:"
 #define D_HOST "主機"
 #define D_HALL_EFFECT "Hall Effect"
+#define D_HEATINDEX "Heat index"
 #define D_HOSTNAME "主機名稱"
 #define D_HUMIDITY "濕度"
 #define D_ILLUMINANCE "照度"
diff --git a/tasmota/my_user_config.h b/tasmota/my_user_config.h
index c4ef41407..04287c238 100644
--- a/tasmota/my_user_config.h
+++ b/tasmota/my_user_config.h
@@ -385,6 +385,8 @@
 //#define MY_LANGUAGE            zh_CN           // Chinese (Simplified) in China
 //#define MY_LANGUAGE            zh_TW           // Chinese (Traditional) in Taiwan
 
+//#define USE_HEAT_INDEX                           // Show calculated Heat index from temperature and humidity (+1k4 code)
+
 // -- Wifi Config tools ---------------------------
 #define WIFI_SOFT_AP_CHANNEL   1                 // Soft Access Point Channel number between 1 and 13 as used by Wi-Fi Manager web GUI
 #define USE_IMPROV                               // Add support for IMPROV serial protocol as used by esp-web-tools (+2k code)
diff --git a/tasmota/tasmota_support/support.ino b/tasmota/tasmota_support/support.ino
index 766a821dc..f6e3b6f55 100755
--- a/tasmota/tasmota_support/support.ino
+++ b/tasmota/tasmota_support/support.ino
@@ -858,6 +858,33 @@ float CalcTempHumToDew(float t, float h) {
   return result;
 }
 
+#ifdef USE_HEAT_INDEX
+float CalcTemHumToHeatIndex(float t, float h) {
+  if (!Settings->flag.temperature_conversion) {                // SetOption8 - Switch between Celsius or Fahrenheit
+    t = t * 1.8f + 32;                                         // Fahrenheit
+  }
+  float hi = 0.5 * (t + 61.0 + ((t - 68.0) * 1.2) + (h * 0.094));
+  if (hi > 79) {
+    float pt = t * t;  // pow(t, 2)
+    float ph = h * h;  // pow(h, 2)
+    hi = -42.379 + 2.04901523 * t + 10.14333127 * h +
+         -0.22475541 * t * h +
+         -0.00683783 * pt +
+         -0.05481717 * ph +
+         0.00122874 * pt * h +
+         0.00085282 * t * ph +
+         -0.00000199 * pt * ph;
+    if ((h < 13) && (t >= 80.0) && (t <= 112.0)) {
+      hi -= ((13.0 - h) * 0.25) * sqrtf((17.0 - abs(t - 95.0)) * 0.05882);
+    }
+    else if ((h > 85.0) && (t >= 80.0) && (t <= 87.0)) {
+      hi += ((h - 85.0) * 0.1) * ((87.0 - t) * 0.2);
+    }
+  }
+  return (Settings->flag.temperature_conversion) ? hi : (hi - 32) / 1.8f;
+}
+#endif  // USE_HEAT_INDEX
+
 float CalcTempHumToAbsHum(float t, float h) {
   if (isnan(t) || isnan(h)) { return NAN; }
   // taken from https://carnotcycle.wordpress.com/2012/08/04/how-to-convert-relative-humidity-to-absolute-humidity/
@@ -1338,13 +1365,19 @@ int ResponseAppendTime(void)
   return ResponseAppendTimeFormat(Settings->flag2.time_format);
 }
 
-int ResponseAppendTHD(float f_temperature, float f_humidity)
-{
+int ResponseAppendTHD(float f_temperature, float f_humidity) {
   float dewpoint = CalcTempHumToDew(f_temperature, f_humidity);
-  return ResponseAppend_P(PSTR("\"" D_JSON_TEMPERATURE "\":%*_f,\"" D_JSON_HUMIDITY "\":%*_f,\"" D_JSON_DEWPOINT "\":%*_f"),
-                          Settings->flag2.temperature_resolution, &f_temperature,
-                          Settings->flag2.humidity_resolution, &f_humidity,
-                          Settings->flag2.temperature_resolution, &dewpoint);
+  int len = ResponseAppend_P(PSTR("\"" D_JSON_TEMPERATURE "\":%*_f,\"" D_JSON_HUMIDITY "\":%*_f,\"" D_JSON_DEWPOINT "\":%*_f"),
+                             Settings->flag2.temperature_resolution, &f_temperature,
+                             Settings->flag2.humidity_resolution, &f_humidity,
+                             Settings->flag2.temperature_resolution, &dewpoint);
+#ifdef USE_HEAT_INDEX
+  float heatindex = CalcTemHumToHeatIndex(TasmotaGlobal.temperature_celsius, TasmotaGlobal.humidity);
+  int len2 = ResponseAppend_P(PSTR(",\"" D_JSON_HEATINDEX "\":%*_f"),
+                              Settings->flag2.temperature_resolution, &heatindex);
+  return len + len2;                              
+#endif  // USE_HEAT_INDEX
+  return len;
 }
 
 int ResponseJsonEnd(void)
diff --git a/tasmota/tasmota_support/support_tasmota.ino b/tasmota/tasmota_support/support_tasmota.ino
index 94c431e86..12406336e 100644
--- a/tasmota/tasmota_support/support_tasmota.ino
+++ b/tasmota/tasmota_support/support_tasmota.ino
@@ -1025,8 +1025,13 @@ bool MqttShowSensor(bool call_show_sensor) {
       }
       if (2 == add_comma) {
         float dewpoint = CalcTempHumToDew(TasmotaGlobal.temperature_celsius, TasmotaGlobal.humidity);
-        ResponseAppend_P(PSTR("%s\"" D_JSON_DEWPOINT "\":%*_f"),
-          (add_comma)?",":"", Settings->flag2.temperature_resolution, &dewpoint);
+        ResponseAppend_P(PSTR(",\"" D_JSON_DEWPOINT "\":%*_f"),
+          Settings->flag2.temperature_resolution, &dewpoint);
+#ifdef USE_HEAT_INDEX
+        float heatindex = CalcTemHumToHeatIndex(TasmotaGlobal.temperature_celsius, TasmotaGlobal.humidity);
+        ResponseAppend_P(PSTR(",\"" D_JSON_HEATINDEX "\":%*_f"),
+          Settings->flag2.temperature_resolution, &heatindex);
+#endif  // USE_HEAT_INDEX
       }
       if (TasmotaGlobal.pressure_hpa != 0) {
         float p = ConvertPressure(TasmotaGlobal.pressure_hpa);
diff --git a/tasmota/tasmota_xdrv_driver/xdrv_01_9_webserver.ino b/tasmota/tasmota_xdrv_driver/xdrv_01_9_webserver.ino
index 1124a60ea..15caa90ab 100644
--- a/tasmota/tasmota_xdrv_driver/xdrv_01_9_webserver.ino
+++ b/tasmota/tasmota_xdrv_driver/xdrv_01_9_webserver.ino
@@ -1027,6 +1027,10 @@ void WSContentSend_THD(const char *types, float f_temperature, float f_humidity)
   WSContentSend_PD(HTTP_SNS_HUM, types, parameter);
   dtostrfd(CalcTempHumToDew(f_temperature, f_humidity), Settings->flag2.temperature_resolution, parameter);
   WSContentSend_PD(HTTP_SNS_DEW, types, parameter, TempUnit());
+#ifdef USE_HEAT_INDEX
+  dtostrfd(CalcTemHumToHeatIndex(f_temperature, f_humidity), Settings->flag2.temperature_resolution, parameter);
+  WSContentSend_PD(HTTP_SNS_HEATINDEX, types, parameter, TempUnit());
+#endif  // USE_HEAT_INDEX
 }
 
 void WSContentEnd(void) {