Drink up, Prague: what the city's summer heat is doing to your body — and how to fight back

Prague recorded its hottest June since meteorological records began in 1961, with the Czech Hydrometeorological Institute logging a mean monthly temperature of 22.4°C across the city — about 3.8 degrees above the long-term average. July is already running hotter. On Wenceslas Square last Tuesday, thermometers hit 36°C by early afternoon. Tourists queued at drinking fountains near the Old Town Hall. Locals grabbed mineral water from Billa on Vinohradská. The question everyone's quietly asking: am I drinking enough, and does it even matter what I drink?

It matters. The Central Bohemian summer has grown measurably more punishing over the past decade. Urban heat island effects in Prague's densely built inner districts — Žižkov, Vinohrady, Nusle — mean pavements retain heat well into the evening, keeping core body temperatures elevated long after sundown. Sweat losses during a moderate 90-minute walk through Riegrovy sady on a 33°C afternoon can exceed one litre. Most people replace far less than that. Mild dehydration — even at 1 to 2 percent of body weight — is enough to blunt concentration, slow reaction time, and tip blood pressure in the wrong direction.

What Prague's wellness scene is actually recommending

The city's nutritional therapists and registered dietitians broadly follow the European Food Safety Authority's 2010 reference values: 2.5 litres of total water daily for men and 2.0 litres for women, from all sources including food. On high-exertion summer days in Prague, those figures climb. The Sports Medicine Clinic at Thomayer University Hospital in Krč advises recreational athletes training outdoors to add roughly 500ml per hour of activity above moderate intensity, adjusted for humidity. A Prague-based wellness programme called Zdravá Praha, run in cooperation with the city's public health authority, has been distributing free hydration guidance cards at community centres across Smíchov and Holešovice since June 2025 — the cards specify electrolyte replenishment, not just water volume.

That electrolyte caveat is important. Drinking large quantities of plain water without sodium and potassium replacement can actually dilute blood electrolytes, a condition called hyponatraemia that presents initially as nausea and headache — symptoms many Praguers mistakenly blame on the heat itself. Sparkling mineral waters from Czech springs help here. Mattoni, sourced from Kyselka in the Karlovy Vary region, contains around 1,050 mg of bicarbonates per litre and sits in nearly every supermarket in Prague for roughly 18 to 22 Czech crowns for a 1.5-litre bottle. Magnesia, another popular Czech brand, offers higher magnesium content — 119 mg per litre — making it a reasonable choice for people who sweat heavily during outdoor exercise.

Beyond the bottle: what you eat counts too

Food contributes roughly 20 to 30 percent of daily water intake. Prague's summer farmers markets are well-positioned to help. The Manifesto Market on Náplavka, open Saturdays through October, currently stocks cucumbers from South Moravian suppliers at 15 crowns apiece — cucumbers run to about 96 percent water by weight. Watermelon, strawberries, and tomatoes from the Jiří z Poděbrad market in Vinohrady cover similar ground. A diet leaning heavily on raw vegetables and fruit during the July heat wave does meaningful hydration work before you've touched a single glass.

Coffee and beer — Prague's two unofficial civic beverages — warrant a more nuanced read than their dehydrating reputation suggests. Moderate caffeine intake, up to around 400 mg daily, does not produce a net fluid loss in habitual consumers, according to a 2014 meta-analysis published in PLOS ONE. A standard double espresso at Café Louvre on Národní třída contributes to your fluid total, not against it. Beer is different: its diuretic effect is real, particularly above 4 percent ABV, and combining alcohol with sustained heat exposure accelerates fluid loss. The Zdravá Praha programme specifically flags afternoon beer gardens as a hydration risk during heat alerts.

The practical upshot is straightforward. Keep a reusable 750ml bottle — several zero-waste shops near Náměstí Míru sell them from around 350 crowns — and refill it three times before 6 pm. Lean on Czech mineral water over plain tap water when physical activity is involved. Eat your water where you can. And if a headache arrives despite drinking steadily, check in with your general practitioner at your local Poliklinika or call the Prague City Health Line before assuming it's just the sun. It might not be.