If you had booked an August holiday in Britain 10 days ago, then heard the weather forecast, you probably would have taken the first train to Gatwick. The forecast for the following week was awful – for storms, clouds, rain and “unseasonably cold” weather. In other words, another typical August. In the event the forecast was wildly inaccurate. Where I was on the Welsh coast, just one day passed without sun for all or part of the day. It did rain heavily for part of one day and there was the odd shower. It certainly was not hot. But a week on the beach was feasible, the sea blue and the sunsets glorious. That we saw relatively few visitors was entirely the result of the forecast, according to local businesses. One publican told me he can predict his takings each day not by the weather but by the 8am forecast. Yet it is so often wrong. The weather forecast is England’s economic sanction against Wales. That August can be changeable is no surprise, but why do we still have our holidays then? Statistically, July is Britain’s hottest month, and June is the sunniest. August is more like May but without the blossoms of spring. Most other countries in the northern hemisphere tend to break in mid-July, which is also when the majority of Americans begin their summer. Southern Europe prefers to go on holiday in August, but that is probably to escape the heat of July, notably this year’s heatwave. August has become a British holiday of habit, thought to relate to the harvest. It was the month when the Industrial Revolution allowed thousands of factory workers to return to their former rural homes to help gather in the crops. The custom continued in London into the 20th century, with East Enders abandoning the gasworks – less needed in summer – and returning to harvest the hops in Kent. August was also the start of the grouse shooting season – not because of the weather but because of the production cycle of a bird. However you slice it, August is simply a bad month for a holiday. By mid-August nights are getting longer and chillier, and the weather ever less predictable. It must make sense to switch to taking leave from mid-June to mid-July. Workers and pupils would get into the open air when it is warmest. Tourist overcrowding would spread and reduce the load on Mediterranean resorts. Working from home is already diversifying work practices. The answer may be to take July off and work partly from home through much of August. Like decimalisation, such a reform of custom and practice requires simply a government with the guts to do it. We know July holidays would make sense for almost everyone. Where does that rank in the reasons for change? Simon Jenkins is a Guardian columnist