{"id":61228,"date":"2026-07-29T18:15:42","date_gmt":"2026-07-29T16:15:42","guid":{"rendered":"https:\/\/alertes-meteo.com\/?page_id=61228"},"modified":"2026-07-29T18:49:38","modified_gmt":"2026-07-29T16:49:38","slug":"indicateur-thermique-national-le-thermometre-du-climat-francais","status":"publish","type":"page","link":"https:\/\/alertes-meteo.com\/index.php\/vagues-de-chaleur-en-france\/indicateur-thermique-national-le-thermometre-du-climat-francais\/","title":{"rendered":"Indicateur thermique national : le thermom\u00e8tre du climat fran\u00e7ais"},"content":{"rendered":"

Quand M\u00e9t\u00e9o-France annonce \u00ab la journ\u00e9e la plus chaude jamais enregistr\u00e9e en France \u00bb ou une vague de froid historique, c\u2019est l\u2019indicateur thermique national qui est en coulisse. Cet indice synth\u00e9tise la temp\u00e9rature moyenne journali\u00e8re de la France m\u00e9tropolitaine \u00e0 partir d\u2019un r\u00e9seau dense de stations de r\u00e9f\u00e9rence, offrant un thermom\u00e8tre fiable du climat national. Dans cet article, nous expliquons ce qu\u2019est l\u2019ITN, comment il est calcul\u00e9, \u00e0 quoi il sert dans la m\u00e9t\u00e9o, la climatologie et la s\u00e9curit\u00e9 civile, et comment vos lecteurs peuvent l\u2019utiliser pour mieux comprendre les pr\u00e9visions et les \u00e9pisodes extr\u00eames.<\/p>\n

Qu\u2019est-ce que l\u2019indicateur thermique national ?<\/h2>\n

L\u2019indicateur thermique national (ITN)<\/strong> est un indice m\u00e9t\u00e9orologique qui repr\u00e9sente la temp\u00e9rature moyenne quotidienne<\/strong> de la France m\u00e9tropolitaine. Il est calcul\u00e9 par M\u00e9t\u00e9o-France depuis 1947 \u00e0 partir de s\u00e9ries homog\u00e9n\u00e9is\u00e9es de temp\u00e9rature minimale et maximale issues d\u2019un r\u00e9seau de stations r\u00e9parties sur tout le territoire. L\u2019ITN ne correspond donc pas \u00e0 la temp\u00e9rature d\u2019une seule ville ni \u00e0 une simple moyenne approximative, mais \u00e0 une synth\u00e8se nationale robuste du climat du jour.<\/p>\n

Temp\u00e9rature moyenne quotidienne : la base de l\u2019ITN<\/h2>\n

Pour construire l\u2019indicateur, M\u00e9t\u00e9o-France utilise la temp\u00e9rature moyenne quotidienne<\/strong>, d\u00e9finie comme la moyenne de la temp\u00e9rature minimale et de la temp\u00e9rature maximale de la journ\u00e9e. Formellement, la temp\u00e9rature moyenne quotidienne TMqTM_q<\/span>T<\/span>M<\/span>q<\/span><\/span><\/span>\u200b<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span> est calcul\u00e9e par TMq=(TNq+TXq)\/2TM_q = (TN_q + TX_q)\/2<\/span>T<\/span>M<\/span>q<\/span><\/span><\/span>\u200b<\/span><\/span><\/span><\/span><\/span>=<\/span><\/span>(<\/span>T<\/span>N<\/span>q<\/span><\/span><\/span>\u200b<\/span><\/span><\/span><\/span><\/span>+<\/span><\/span>T<\/span>X<\/span>q<\/span><\/span><\/span>\u200b<\/span><\/span><\/span><\/span><\/span>)<\/span>\/2<\/span><\/span><\/span><\/span>. Cette moyenne est ensuite agr\u00e9g\u00e9e sur un ensemble de stations de r\u00e9f\u00e9rence afin de fournir une valeur unique pour la France m\u00e9tropolitaine.<\/p>\n

Comment l\u2019ITN est-il calcul\u00e9 ?<\/h2>\n

Contrairement \u00e0 l\u2019id\u00e9e d\u2019une moyenne de quelques stations urbaines, l\u2019ITN repose sur une s\u00e9lection de 30 stations m\u00e9t\u00e9orologiques de r\u00e9f\u00e9rence<\/strong>, choisies pour la qualit\u00e9, la longueur et l\u2019homog\u00e9n\u00e9it\u00e9 de leurs s\u00e9ries. Ces stations sont r\u00e9parties de mani\u00e8re \u00e9quilibr\u00e9e<\/strong> sur le territoire, des plaines de l\u2019ouest aux vall\u00e9es alpines, afin de refl\u00e9ter au mieux le climat moyen du pays.<\/p>\n

L\u2019indicateur est obtenu en faisant la moyenne des temp\u00e9ratures moyennes quotidiennes de ces 30 stations, selon une pond\u00e9ration prenant en compte leur repr\u00e9sentativit\u00e9 g\u00e9ographique et altitudinale. Les s\u00e9ries sont homog\u00e9n\u00e9is\u00e9es pour corriger les \u00e9ventuelles ruptures li\u00e9es aux d\u00e9placements de postes, aux changements d\u2019instruments ou \u00e0 l\u2019urbanisation, ce qui garantit un suivi fiable des tendances climatiques \u00e0 long terme.<\/p>\n

Un outil co-construit et norm\u00e9<\/h2>\n

Historiquement, l\u2019ITN a \u00e9t\u00e9 d\u00e9velopp\u00e9 conjointement par M\u00e9t\u00e9o-France et EDF pour anticiper les besoins \u00e9lectriques en fonction des temp\u00e9ratures, avant de devenir un marqueur central pour la climatologie fran\u00e7aise. Les stations utilis\u00e9es r\u00e9pondent aux normes internationales de l\u2019Organisation m\u00e9t\u00e9orologique mondiale (OMM) pour limiter l\u2019impact des \u00eelots de chaleur urbains, avec des abris install\u00e9s sur des surfaces d\u00e9gag\u00e9es, \u00e0 distance des sources de chaleur artificielles.<\/p>\n<\/div>\n

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\n

Indicateur thermique national annuel en France depuis 1947<\/h2>\n

Temp\u00e9rature moyenne annuelle de la France m\u00e9tropolitaine<\/p>\n <\/div>\n\n

\n Normale 1991-2020<\/span>\n 12,98\u00a0\u00b0C<\/strong>\n <\/div>\n\n
\n Cliquez sur une barre pour afficher l\u2019ann\u00e9e, la temp\u00e9rature et l\u2019\u00e9cart \u00e0 la normale.\n <\/div>\n\n
\n
\n \n Indicateur thermique national annuel en France de 1947 \u00e0 2025<\/title>\n <desc>\n Histogramme de la temp\u00e9rature moyenne annuelle nationale. Les ann\u00e9es plus\n chaudes que la normale 1991-2020 sont rouges et les ann\u00e9es plus froides sont bleues.\n Chaque barre est interactive.\n <\/desc>\n <\/svg>\n <div class=\"itnfr-tooltip\" data-itnfr-tooltip role=\"status\" aria-hidden=\"true\"><\/div>\n <\/div>\n <\/div>\n\n <div class=\"itnfr-legend\" aria-label=\"L\u00e9gende\">\n <span><i class=\"itnfr-dot itnfr-dot-positive\"><\/i> Ann\u00e9e plus chaude que la normale<\/span>\n <span><i class=\"itnfr-dot itnfr-dot-negative\"><\/i> Ann\u00e9e plus froide que la normale<\/span>\n <span><i class=\"itnfr-line-sample\"><\/i> Ligne de la normale 1991-2020<\/span>\n <\/div>\n\n <p class=\"itnfr-definition\">\n L\u2019indicateur thermique national (ITN) est la moyenne des temp\u00e9ratures minimales\n et maximales mesur\u00e9es dans 30 stations r\u00e9parties de fa\u00e7on \u00e9quilibr\u00e9e en France\n m\u00e9tropolitaine. Il fournit une temp\u00e9rature moyenne repr\u00e9sentative du pays.\n <\/p>\n\n <p class=\"itnfr-note\">\n L\u2019ann\u00e9e 2026 n\u2019est pas incluse, car elle est encore en cours. 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25,\n class: \"itnfr-x-label\"\n });\n label.textContent = year;\n labelsGroup.appendChild(label);\n });\n svg.appendChild(labelsGroup);\n\n svg.addEventListener(\"click\", (event) => {\n if (event.target === svg || event.target.classList.contains(\"itnfr-grid-line\")) {\n removeSelection();\n hideTooltip();\n }\n });\n });\n })();\n<\/script><div class=\"fusion-separator fusion-full-width-sep\" style=\"align-self: center;margin-left: auto;margin-right: auto;width:100%;\"><div class=\"fusion-separator-border sep-double\" style=\"--awb-height:20px;--awb-amount:20px;--awb-sep-color:#ffffff;border-color:#ffffff;border-top-width:1px;border-bottom-width:1px;\"><\/div><\/div><script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-8902396130105212\"\n crossorigin=\"anonymous\"><\/script>\n<!-- bas de page -->\n<ins class=\"adsbygoogle\"\n style=\"display:block\"\n data-ad-client=\"ca-pub-8902396130105212\"\n data-ad-slot=\"7724440717\"\n data-ad-format=\"auto\"\n data-full-width-responsive=\"true\"><\/ins>\n<script>\n (adsbygoogle = window.adsbygoogle || []).push({});\n<\/script><div class=\"fusion-text fusion-text-2\"><h2 id=\"quoi-sert-lindicateur-thermique-national\" class=\"font-semibold leading-tight text-pretty mb-2 mt-4 [.has-inline-images_&]:clear-end text-lg first:mt-0 md:text-lg [hr+&]:mt-4\">\u00c0 quoi sert l\u2019indicateur thermique national ?<\/h2>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\">L\u2019ITN est un outil polyvalent au c\u0153ur de plusieurs usages : <strong>pr\u00e9visions m\u00e9t\u00e9o<\/strong>, <strong>diagnostic des vagues de chaleur<\/strong>, <strong>suivi des \u00e9pisodes froids<\/strong>, <strong>bilans climatiques mensuels et annuels<\/strong>. Pour les pr\u00e9visionnistes, il permet de qualifier rapidement la situation thermique du pays, d\u2019anticiper les contrastes et de communiquer simplement avec le grand public.<\/p>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\">En cas de <strong>vague de chaleur<\/strong>, l\u2019ITN est l\u2019un des crit\u00e8res utilis\u00e9s pour d\u00e9finir officiellement l\u2019\u00e9v\u00e9nement : en France, une vague de chaleur est caract\u00e9ris\u00e9e lorsque l\u2019indicateur d\u00e9passe certains seuils (autour de 25 \u00b0C sur une journ\u00e9e ou de 23\u201324 \u00b0C pendant plusieurs jours cons\u00e9cutifs). De la m\u00eame mani\u00e8re, des valeurs tr\u00e8s basses de l\u2019ITN permettent de d\u00e9tecter et de qualifier des \u00e9pisodes de froid exceptionnel, comme la nuit d\u2019avril 2022 la plus froide pour un mois d\u2019avril depuis 1947.<\/p>\n<h2 id=\"un-thermomtre-du-changement-climatique\" class=\"font-semibold leading-tight text-pretty mb-2 mt-4 [.has-inline-images_&]:clear-end text-base first:mt-0\">Un thermom\u00e8tre du changement climatique<\/h2>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\">Sur des p\u00e9riodes longues, l\u2019\u00e9volution de l\u2019ITN annuel ou saisonnier met en \u00e9vidence le <strong>r\u00e9chauffement climatique<\/strong> en France, avec une hausse de la temp\u00e9rature moyenne d\u2019environ 1,6 \u00b0C par rapport au d\u00e9but du XX\u1d49 si\u00e8cle selon les \u00e9tudes climatologiques. Utilis\u00e9 avec les normales 1991\u20132020, l\u2019indicateur thermique permet d\u2019objectiver les anomalies chaudes ou froides et de replacer chaque ann\u00e9e dans la trajectoire climatique du pays.<\/p>\n<h2 id=\"itn-vagues-de-chaleur-et-scurit-civile\" class=\"font-semibold leading-tight text-pretty mb-2 mt-4 [.has-inline-images_&]:clear-end text-lg first:mt-0 md:text-lg [hr+&]:mt-4\">ITN, vagues de chaleur et s\u00e9curit\u00e9 civile<\/h2>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\">Du point de vue de la <strong>s\u00e9curit\u00e9 civile<\/strong>, l\u2019ITN est pr\u00e9cieux pour d\u00e9clencher et adapter les dispositifs de vigilance lors des \u00e9pisodes de <strong>vagues de chaleur<\/strong> ou de froid intense. Un ITN tr\u00e8s \u00e9lev\u00e9 sur plusieurs jours signifie que la chaleur est g\u00e9n\u00e9ralis\u00e9e, au-del\u00e0 des habituelles disparit\u00e9s r\u00e9gionales, ce qui renforce les impacts sur la sant\u00e9, le syst\u00e8me \u00e9lectrique, les r\u00e9seaux de transport et les activit\u00e9s de plein air.<\/p>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\">Pour les citoyens, les touristes et les professionnels du tourisme, suivre l\u2019ITN aide \u00e0 comprendre pourquoi une semaine peut \u00eatre jug\u00e9e \u00ab exceptionnellement chaude \u00bb \u00e0 l\u2019\u00e9chelle nationale, m\u00eame si les ressentis varient d\u2019une r\u00e9gion \u00e0 l\u2019autre. Les offices de tourisme, les organisateurs d\u2019\u00e9v\u00e9nements ext\u00e9rieurs ou les gestionnaires d\u2019h\u00e9bergements peuvent int\u00e9grer ces informations dans leurs strat\u00e9gies de communication et de pr\u00e9vention.<\/p>\n<h2 id=\"comment-utiliser-litn-dans-les-prvisions-et-au-quo\" class=\"font-semibold leading-tight text-pretty mb-2 mt-4 [.has-inline-images_&]:clear-end text-lg first:mt-0 md:text-lg [hr+&]:mt-4\">Comment utiliser l\u2019ITN dans les pr\u00e9visions et au quotidien ?<\/h2>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\">Sur un site sp\u00e9cialis\u00e9 m\u00e9t\u00e9o, l\u2019ITN peut \u00eatre int\u00e9gr\u00e9 dans les <strong>pages de pr\u00e9visions nationales<\/strong>, les <strong>bilans m\u00e9t\u00e9o<\/strong>, les dossiers p\u00e9dagogiques sur la <strong>canicule<\/strong> ou les <strong>vagues de froid<\/strong>. En tant qu\u2019utilisateur, il sert \u00e0 r\u00e9pondre \u00e0 des questions simples : \u00ab La France conna\u00eet-elle actuellement une chaleur exceptionnelle ? \u00bb, \u00ab Cet \u00e9pisode est-il comparable aux grandes canicules pass\u00e9es ? \u00bb.<\/p>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\">Pour vos lecteurs, quelques usages concrets :<\/p>\n<ul class=\"marker:text-quiet list-disc pl-8\">\n<li class=\"py-0 my-0 prose-p:pt-0 prose-p:mb-2 prose-p:my-0 [&>p]:pt-0 [&>p]:mb-2 [&>p]:my-0\">\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\">Visualiser les <strong>records<\/strong> de chaleur ou de froid et les comparer \u00e0 l\u2019ann\u00e9e en cours.<\/p>\n<\/li>\n<li class=\"py-0 my-0 prose-p:pt-0 prose-p:mb-2 prose-p:my-0 [&>p]:pt-0 [&>p]:mb-2 [&>p]:my-0\">\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\">Comprendre les annonces de M\u00e9t\u00e9o-France sur les \u00ab journ\u00e9es les plus chaudes jamais enregistr\u00e9es \u00bb ou les \u00e9pisodes froids historiques.<\/p>\n<\/li>\n<li class=\"py-0 my-0 prose-p:pt-0 prose-p:mb-2 prose-p:my-0 [&>p]:pt-0 [&>p]:mb-2 [&>p]:my-0\">\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\">Relier l\u2019ITN aux <strong>impacts ressentis localement<\/strong> : nuits tropicales, canicule, difficult\u00e9s pour les activit\u00e9s de plein air, surcharge des r\u00e9seaux.<\/p>\n<\/li>\n<\/ul>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\">En maillage interne, il est pertinent de proposer des liens vers vos pages \u00ab <strong>Canicule<\/strong> \u00bb, \u00ab <strong>Nuits tropicales<\/strong> \u00bb, \u00ab <strong>Pr\u00e9visions m\u00e9t\u00e9o \u00e0 15 jours<\/strong> \u00bb et \u00ab <strong>Climat pass\u00e9 et futur<\/strong> \u00bb afin d\u2019augmenter le temps de lecture et d\u2019offrir une vision coh\u00e9rente du risque thermique.<\/p>\n<h2 id=\"faq-seo--indicateur-thermique-national\" class=\"font-semibold leading-tight text-pretty mb-2 mt-4 [.has-inline-images_&]:clear-end text-lg first:mt-0 md:text-lg [hr+&]:mt-4\">FAQ SEO \u2013 Indicateur thermique national<\/h2>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\"><strong>1. Qu\u2019est-ce que l\u2019indicateur thermique national (ITN) ?<\/strong><br \/>\nL\u2019ITN est la moyenne quotidienne des temp\u00e9ratures en France m\u00e9tropolitaine, calcul\u00e9e par M\u00e9t\u00e9o-France \u00e0 partir de 30 stations de r\u00e9f\u00e9rence r\u00e9parties sur tout le territoire.<\/p>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\"><strong>2. Comment M\u00e9t\u00e9o-France calcule-t-elle l\u2019ITN ?<\/strong><br \/>\nChaque jour, on calcule la temp\u00e9rature moyenne quotidienne dans chaque station (moyenne de la minimale et de la maximale), puis on fait la moyenne de ces valeurs sur 30 stations homog\u00e9n\u00e9is\u00e9es et repr\u00e9sentatives du climat fran\u00e7ais.<\/p>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\"><strong>3. L\u2019ITN sert-il \u00e0 d\u00e9finir une vague de chaleur ?<\/strong><br \/>\nOui, l\u2019ITN est un crit\u00e8re cl\u00e9 pour caract\u00e9riser les vagues de chaleur : au-del\u00e0 de certains seuils pendant plusieurs jours, il confirme une situation de fortes chaleurs g\u00e9n\u00e9ralis\u00e9es en France.<\/p>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\"><strong>4. L\u2019indicateur thermique national mesure-t-il le r\u00e9chauffement climatique ?<\/strong><br \/>\nIl permet de suivre l\u2019\u00e9volution des temp\u00e9ratures et les anomalies par rapport aux normales 1991\u20132020, mais les \u00e9tudes de r\u00e9chauffement utilisent en compl\u00e9ment d\u2019autres outils climatologiques.<\/p>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\"><strong>5. L\u2019ITN est-il influenc\u00e9 par les \u00eelots de chaleur urbains ?<\/strong><br \/>\nLes stations de l\u2019indicateur respectent des normes strictes de mesure et sont g\u00e9n\u00e9ralement implant\u00e9es sur des terrains d\u00e9gag\u00e9s, m\u00eame si certaines sont devenues p\u00e9riurbaines avec l\u2019expansion des villes.<\/p>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\"><strong>6. O\u00f9 peut-on consulter des graphiques de l\u2019ITN ?<\/strong><br \/>\nDes graphiques annuels et mensuels sont disponibles sur des plateformes ouvertes de donn\u00e9es climatiques et sur certains sites m\u00e9t\u00e9o qui r\u00e9utilisent officiellement les s\u00e9ries M\u00e9t\u00e9o-France.<\/p>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\"><strong>7. Quelle est la diff\u00e9rence entre ITN et temp\u00e9rature relev\u00e9e dans ma ville ?<\/strong><br \/>\nL\u2019ITN est une moyenne nationale ; votre ville peut \u00eatre plus chaude ou plus froide selon la situation locale, la topographie et l\u2019urbanisation, m\u00eame lorsque l\u2019ITN indique une anomalie marqu\u00e9e.<\/p>\n<p class=\"my-2 [&+p]:mt-4 [&_strong:has(+br)]:inline-block [&_strong:has(+br)]:align-top\">L\u2019indicateur thermique national est bien plus qu\u2019un simple chiffre : c\u2019est le <strong>thermom\u00e8tre du climat fran\u00e7ais<\/strong>, au croisement de la m\u00e9t\u00e9orologie op\u00e9rationnelle, de la climatologie et de la s\u00e9curit\u00e9 civile. En l\u2019int\u00e9grant \u00e0 vos contenus, vous offrez \u00e0 vos lecteurs une cl\u00e9 de lecture puissante pour comprendre les vagues de chaleur, les \u00e9pisodes froids et la trajectoire du r\u00e9chauffement en France, tout en renfor\u00e7ant la cr\u00e9dibilit\u00e9 scientifique de votre site.<\/p>\n<\/div><div class=\"fusion-separator fusion-full-width-sep\" style=\"align-self: center;margin-left: auto;margin-right: auto;width:100%;\"><div class=\"fusion-separator-border sep-double\" style=\"--awb-height:20px;--awb-amount:20px;border-color:var(--awb-color3);border-top-width:1px;border-bottom-width:1px;\"><\/div><\/div><div class=\"fusion-builder-row fusion-builder-row-inner fusion-row fusion-flex-align-items-flex-start fusion-flex-content-wrap\" style=\"--awb-flex-grow:0;--awb-flex-grow-medium:0;--awb-flex-grow-small:0;--awb-flex-shrink:0;--awb-flex-shrink-medium:0;--awb-flex-shrink-small:0;width:105% !important;max-width:105% !important;margin-left: calc(-5% \/ 2 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