A serious scientific examination into when iced-coffee season actually starts

When London found itself in a flash of 20C heat last month, one question came up more than others. It wasn’t about beer gardens or sitting on Primrose Hill. It wasn’t even about Aperol. No. It was about something deeper, something more important. It was something that would tug on the heartstrings of each and every Londoner.

Could this be the start of iced-coffee season? 

We were forced to rethink when snow (yes, snow) showed up just days later. But the capital’s yo-yo weather only underlined the question: when is the precise moment to swap your oat flat white for an iced americano? That’s why we’ve undertaken a detailed and extremely serious investigation into when London’s iced-coffee season properly begins.

The basics

First, we must address the difference between iced coffee and cold-brew coffee. The former is made by brewing coffee hot and pouring it over ice to serve. The latter, widely considered to be higher-brow, is made by brewing coffee with cold water, leaving it for at least 12 hours, and then serving it over ice. For the purpose of this article, we’re talking about your OG ‘iced coffee’. The type that’s an accessory in itself, makes that distinct slurping sound and creates mesmerising swirls when milk is poured in. Icy. 

Let’s take a look at the cold, hard data. An analysis of Google searches for ‘iced coffee’ over the last five years in the UK shows that interest peaked in the week beginning July 18, 2021. In that same week, we saw temperature highs of around 31C, and for the first time ever, extreme amber heat warnings were issued by the Met Office.

The second highest peak of searches for iced coffee took place in the week beginning April 5, 2020, when interest was 54 percent less. That week saw a temperature high of 24C and was also the start of the first nationwide lockdown: people were bored, making iced coffee seemed like a semi-fun, holiday-type activity. Articles published that week also show that this was when the TikTok whipped coffee trend (also known as ‘dalgona coffee’, which also happens to be served over ice), was alive and kicking. The caffeine world works in mysterious ways. 

The trend

Image: Jamie Inglis / Time Out London

A quick glance at our very detailed graph confirms that interest in iced coffee typically correlates with warmer months, with the lowest interest usually taking place from November to February (well, duh!). 

Climpson and Sons’ café manager, Joel Darville, says that their sales more or less reflect this. Climpson’s official cold coffee season starts in mid-April (around Easter), whatever the weather. Between April 1 and October 20 last year, their biggest sellers were flat whites and lattes, but there continued to be huge spikes for cold coffees on very hot days.

Sophie Chow, Pret’s UK head of commercial, saw a similar pattern in Pret’s sales. ‘If we have a random week of hot weather, like we did in March, we can see our iced drinks sales double or even triple in a week,’ she says. ‘As a rule, though, the season starts with summer. Our iced coffee sales begin to lift from May and remain consistently higher through to the end of September.’ Over half of Pret’s iced drinks (iced lattes are the most popular) are sold over June, July and August, a trend reflected in almost all of their UK stores.

Okay, this is pretty unsurprising. But iced coffee season is also directly linked to popular culture. Google searches for ‘iced coffee’ start to incline in late March and typically peak in late July, which happens to be when the ‘Love Island’ final takes place.

This trend was skewed only in 2020: most likely thanks to TikTok’s whipped coffee, the pandemic, and the fact that the ‘Love Island’ summer series was cancelled. It might not seem like the most scientific conclusion, but we do know that the reality show has historically popularised the icy beverage. 

The science

It doesn’t take a genius to work out that public interest in iced coffee relates to how hot it is outside. But there’s actually a whole other surprising dimension to it that’s less obvious. To find out more, we spoke to Christopher Hendon, professor of chemistry at the University of Oregon and author of ‘Water for Coffee’ (he’s also known as ‘Dr Coffee’).

‘You tend to perceive more flavours in beverages when they’re closer to the temperature of your mouth,’ Hendon says. ‘It’s this idea of temperature differentials. For example, water freezes at 0C, liquid coffee is going to be above zero: let’s say an iced coffee is 30C. A hot coffee could be served at 80C. So, in the worst-case scenario, an iced coffee will only ever be 30C away from your body temperature [which is on average 37C]. You’ll tend to taste some of the flavours that you can’t taste in hot brewed coffee, simply because they’re not available to you.’

This is interesting for two reasons. One: if a coffee doesn’t taste good cold, chances are it’s just shit coffee. Two: people who drink iced coffee all year round are probably on to something.

The market 

Now that all that science is cleared up, it’s time for some closer market analysis. We spoke to two other London coffee chains to get their take on when iced-coffee season starts (you can’t argue with the market, after all). 

We already know that Pret and Climpson’s have reasonably predictable iced-coffee sales. But according to a spokesperson from Starbucks, their cold beverages have gained year-round popularity – so it seems like their Instagram-able cup design is doing something. Starbucks said: ‘In the four years up until 2021, Starbucks saw cold beverages grow by nearly 45 percent worldwide, with millennials and Gen Z-ers twice as likely to choose cold coffee.’

Meanwhile, Jamie Strachan, head of coffee at Dark Arts Coffee, says that their iced coffee orders tend to spike around the third week of March – and that popularity in general has taken off in recent years. ‘There was a period of time when only espresso or filter was [considered] real coffee, and people were a bit embarrassed about iced drinks,’ Strachan says. ‘Now, a lot of the pretence has gone.’

The coffee conundrum

While the figures show that iced coffee generally comes out of hibernation in spring, there’s still something to be said about the fact that most coffee shops sell it year-round. 

‘[For me] iced coffee season is every season – I get an iced latte every day of the year,’ says research associate and iced coffee enthusiast Nathalie Nourry. ‘I hate hot coffee; I let it stand there all day until it gets cold. Iced coffee is fine because it’s cold in the first place.’ 

Many people consider iced coffee to be the ‘gateway coffee’, an easy-drinking caffeine hit, or – as is the case with iced fraps in particular – a coffee which is dangerously close to a dessert. There have even been links drawn between year-round iced coffee drinking and counterculture in the LGBTQ+ community.

‘Gays will do ridiculous things and there’s something so counterculture about drinking an iced coffee during the winter,’ an article in GQ quotes. ‘Essentially, iced coffee has become a queer avatar, and a way for gay people to signpost themselves against the uniformity of heterosexuality,’ it continues.

As for when iced coffee season officially ends? Caitlin Doyle, a bartender and a passionate iced coffee drinker (order: a Caffè Nero semi-skimmed iced latte), believes she has the answer. ‘Iced coffee season ends when Pumpkin Spice Latte season begins,’ Doyle says.

Pumpkin-spiced lattes became available in UK Starbucks stores on September 2, 2021. That same week, Google searches for ‘iced coffee’ in the UK decreased by 5 percent from the week before, before continuing on a steep decline into the autumn months. See? Everything is connected. 

To conclude the investigation ‘When does iced coffee season actually start?’, we have two sets of results. Based on sales figures, average temperatures, search interest and expert coffee opinions, the scientific answer is usually the final week of March. The season then peaks in the fourth week of July before trailing off in the first week of September. Iced-coffee season is, technically, already here. 

But the real answer? Iced-coffee season starts whenever you want it to. 

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