Andrea Felsted is a Bloomberg Gadfly columnist covering the consumer and retail industries. She previously worked at the Financial Times.

Reports last week of a huge retail sales jump gave us all a bit of cheer about the U.K. outlook. Well, it's Monday, and here's the cold water.

A burst of hot weather last month sent consumers scurrying to the shops for off-the-shoulder dresses, frayed-hem jeans and summer sandals, producing a 1.4 percent increase in the volume of retail sales compared with June, the best for that month since 2002.

That's great news for retailers. It's less helpful if you're trying to figure out the impact of Britain's vote to leave the EU on the U.K. economy. Changing shopping habits and swings in weather-related risks complicate the underlying picture, and we might not get a decent sense of the true state of the post-Brexit consumer until the holiday season. 

To be sure, weather's often used as an excuse for poor sales. As former Marks & Spencer Chief Executive Stuart Rose once quipped, "weather is for wimps." But there are legitimate reasons why the climate can help or hinder sales. 

Big Chill? You Wish.
Milder autumns in the past two years weighed on U.K. clothing and shoe sales
Source: U.K. Office for National Statistics

To start with, consumers are much more spontaneous than they used to be. The advent of internet shopping, particularly next-day and same-day delivery, means that when they want new clothes, they want them immediately. In the past, shoppers would have planned their purchases, stocking up at the start of the season. 

That means people won't shop for winter coats, for example, until the bad weather actually arrives. This makes retailers much more vulnerable to swings in weather conditions, or changes in the timing of bank holidays or school holidays, from one year to the next.

This year, July's heatwave came after many retailers, including Next, Debenhams and M&S, had started their summer sales. So the sales spike from people flocking to buy new shorts won't bring such a big lift to profits.

Weather Forecast
Shares in U.K. retailer Next partly reflect warnings on weather-related hits to demand for clothing
Source: Bloomberg

And the weather doesn't just affect demand for clothing. DIY chain Kingfisher said last week that warmer temperatures sent U.K. sales of seasonal items, such as bedding plants, sprinklers and decking, up 10 percent from a year ago.

While the effect of the weather should balance out over a full year, in the short term, it can affect the timing of spending, and even whether consumers choose to spend at all.

So where does that leave those looking for a clue about the effect of Brexit on consumers?

The autumn, with back-to-school and Halloween shopping, could be hard to read. The last two autumns have been unusually warm, and prompted some shoppers to hold off from buying new winter coats and cosy cardigans.  Last year H&M was among retailers saying a warm third quarter across Europe weighed on demand for clothing, including at its British shops.

If there's a cold snap -- particularly if it comes early in the season -- that could boost demand for outerwear and sweaters, and then sales figures could look rosy once more. But if the weather stays warm and consumers stay away from the shops, it'll be hard to tell if that's due to post-Brexit jitters or to Brits just doing their usual thing of not buying items until they're needed. 

So that leaves holiday spending as the big test of post-Brexit consumer strength. The so-called golden quarter, containing the Christmas and New Year periods, is always an important period: it can account for half of non-food retailers' annual profit.

This year, the festive season will be crucial for judging consumers' strength, and even that involves a bit of a wait -- the Office for National Statistics doesn't publish its December retail sales data until Jan. 20. 

There's even more riding on this year's holiday season than usual.

This column does not necessarily reflect the opinion of Bloomberg LP and its owners.

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Andrea Felsted in London at

To contact the editor responsible for this story:
Jennifer Ryan at