Okay, so it's hot and you want an ice-cream. That seems obvious, but what is less obvious is the breakdown of different ice-cream types sold in differing weather. For instance in moderate warmth a soft ice-cream in a cone is sold more. However if it starts to get really hot people tend to look for something more thirst quenching such as an ice lolly, which is effectively a drink on a stick.
Lager has a threshold of 73 degrees Fahrenheit,  when the temperatures reach this level sales of Lager start to go through the roof. Sausages also sell well in hot weather due to the abundance these days of the back garden barbecue. Cold weather tends to increase the sale of meat and potatoes, along with soups and hot chocolate.
The Indian monsoon brings a huge rise in the sale of Umbrellas, and T-shirts and shorts are purchased en masse in Mediterranean  resorts. As temperatures drop sharply on a cold January evening millions of householders click the thermostat and get the heating on, adding to the toll on the gas and electricity stations scattered around the country.  So when the power industry orders its supplies from various sources it is dependent on the medium term weather forecast to ensure they can provide for any anticipated demand.
Farmers have key decisions to make based on the weather. They can spend tens of thousands of pounds on fertilisers and anti-fungal sprays. If it rains within approximately four to six hours of application then all the benefits, and thus thousands of pounds, can be lost. Other problems that can occur for farmers is the onset of various pests and diseases which can thrive under certain climatic conditions. As an example, potato blight occurs when the weather is warm and damp.
Some farmers use their own instincts and experience to forecast the weather, whereas more and more turn to science using the meteorological office services, or investing in their own weather stations to record rain, wind, temperature, pressure etc
The commercial airline industry is also clearly subject to climatic influences. Aircraft flying from the US to Britain seek out the strong ribbon of air blowing from west to east at around 30,000 feet, known as the jet stream. Planes flying in the opposite direction avoid the jet stream. As a consequence the flight from east to west can be substantially quicker! Upper air temperatures also affect the efficiency of the engines, so reliable temperature data is essential. The world's airline industry saves many hundreds of millions of pounds (or dollars) per year by utilising the weather for the greatest benefit.
The water industry is another obvious business that is influenced by the climate. In times of drought measures have to be put in place to preserve the water supply, and when we have a wet spell then the rain has to be trapped and stored in aquifers (giant water bearing rocks which hold vast amounts of water) and reservoirs. When the water starts to run out extreme measures such as hose pipe bans are implemented. The irony of course being that we most need water at the times when it is least available. The British summer of 1976 is one that will long stick in the memory for this exact reason.
We can see therefore that the Climate has a direct and really quite obvious effect on business, but also can have a much larger impact but in a less direct, subtle way.