Increase in floods during summer months, analysis reveals

Over a third (35%) of home insurance flood claims occur between June and August, according to new analysis from insurer, Aviva¹.

Examination of the insurer’s home and commercial property flood claims data from 2013-2024 reveals that - with the exception of December which accounts for 17% of claims – most floods occur during July and August (each accounting for 12% of total flood claims), with June also proving a peak month for home insurance claims. 

The data also reveals a trend towards an increased likelihood of floods occurring outside of traditional ‘flood season’ – typically October to March - and in the summer months. While 2013, 2014 and 2015 saw some flooding in the summer, most claims occurred during the winter months. However, in five out of the last ten years, (2016, 2018, 2020, 2021 and 2022), Aviva received the most flood claims during the summer, with significant spikes in August 2020 and July 2021.  

Although winter floods tend to be caused by rivers bursting their banks after prolonged periods of rain where the ground is already saturated, floods during the summer are often caused by heavy, intense and slow-moving downpours falling onto dry ground following hot, dry weather. 

Jason Storah, CEO UK & Ireland General Insurance at Aviva, said: “Traditionally, we think of floods happening in the autumn and winter, when rainfall occurs over a period of time and rivers reach capacity. However, this analysis shows that floods can and do occur at any time and summer flash floods are becoming more commonplace. 

“This pattern of flood claims suggests that residents and businesses should be prepared for floods at any point during the year and put in place a flood action plan.  

“Whilst residents and business owners may be more aware of the risks to their properties if they are close to a body of water, one in five properties is at risk from surface water or flash floods which can be unexpected, particularly when we’ve experienced hot, dry days.

“Flash floods can catch us off guard as they are sudden and harder to predict, so we’d urge people to get ready and take action to protect their homes or businesses. This can mean simple things like moving sentimental items to higher levels or installing flood gates at their properties. As urban areas can be particularly susceptible to flash floods, we’d also encourage people to consider their outside spaces, ideally including permeable materials such as lawn, plants or softer landscaping materials like gravel to help water to drain.”

Changes to outside spaces may increase flash flood risk

According to research commissioned by Aviva among 2,004 homeowners3, over a quarter (27%) of UK homeowners have already or plan to replace part or all of their garden with a driveway made from non-permeable material. A further 21% would consider making the change. And a fifth (21%) have already switched their natural lawn with artificial grass or plan to, with a further 19% considering the swap. 

However, impermeable surfaces and a lack of soil and natural planting make it more difficult for water to soak away, which can overwhelm drains and cause flooding. 

Regional differences

In addition to seasonal variations, the data also suggests differences in the places where floods occur between the summer and winter months. In winter, floods are more common in the North West, South West and Northern England, which also typically experience river flooding. However, the summer months see a peak in flash flood claims in Greater London, the South East and the East of England. 

Storah added: “Sadly, changing weather patterns and extreme weather such as flash flooding in the summer are things we are likely to experience more often, so it’s important that our properties are climate-ready, regardless of where we live or work.”

Aviva has developed the following advice to help residents and business owners make their outside spaces more flood resilient:

• Choose more permeable materials such as gravel or block paving. Using permeable materials – that allow rainwater to soak through to the soil below – can help reduce the risk from surface water flooding. 
• Check if you need planning permission – you may need planning permission if you to intend to change an area of more than five square metres using non-permeable material.
• Keep drains clear – check the drains around your property regularly and ensure they are free of leaves, gravel or mud.  Report any blocked public road drains or culverts to your local council or authority.
• Consider making partial changes – having a border around a driveway or installing a drain will help rainwater to run off during heavy downpours, reducing the flow of water into street drains, and may help stop water from entering your property. Or consider using more permeable materials in part of your outside space to help with drainage.
• Collect rainwater – consider installing a water butt or other rainwater collection device to prevent water from overwhelming drains. Plants and wildlife prefer rainwater to tap water too and during droughts, rainwater collection devices can help to save water.
• Check your home’s flood risk – even if your home is nowhere near a river or the sea, it could still be at risk from flooding, so check your home’s status with the Environment Agency.

More advice and information about flooding and flood resilience can be found in Aviva’s Building Future Communities report.

-Ends-

References:

^{1. Analysis of Aviva commercial and personal property flood claims data 2013-2024 (year to date).}

^{2. Aviva flood mapping data.}

^{3. Research conducted by Censuswide on behalf of Aviva among 2004 UK homeowners August 2023.}

Media enquiries: