Hot weather driving: dangers and risks

Warm summer conditions are often seen as ideal for driving in New Zealand, but hot weather brings its own set of risks. High temperatures can affect road surfaces, vehicle systems, fuel consumption, and fire risk, particularly on rural and regional roads. Understanding how heat impacts your vehicle can help reduce breakdowns, improve safety, and avoid costly problems during the Kiwi summer.

Tar Bleed

Tar bleed is a common issue on New Zealand roads during prolonged hot weather. As temperatures rise, bitumen can soften and rise to the surface, creating shiny black patches that significantly reduce tyre grip.

Tar bleed is most likely to occur:

• On rural and provincial roads
• On chipseal surfaces
• During heatwaves and extended dry periods
• On roads with low traffic volumes

Drivers may not notice the loss of grip until braking or cornering, where stopping distances can suddenly increase. This is especially hazardous for heavy vehicles, motorcycles, and vehicles towing trailers.

Increased Risk of Vehicle Fires in Dry Conditions

Dry summer conditions increase the risk of fires caused by vehicles, particularly in rural areas. Exhaust systems, catalytic converters, and diesel particulate filters can reach extremely high temperatures. If these components come into contact with dry grass, leaves, or roadside debris, ignition can occur.

High-risk situations include:

• Parking on dry grass at rural pull-off areas
• Stopping beside paddocks, forestry roads, or construction sites
• Driving through long grass where debris can build up underneath the vehicle

This risk is especially relevant for utes, trucks, and vehicles operating in farming, forestry, and construction environments.

Higher Fuel Consumption from Air Conditioning Use

During summer, air conditioning is often used continuously, particularly in urban traffic or during long-distance travel. Air conditioning systems increase engine load, which can result in higher fuel consumption.

Fuel use can increase due to:

• Continuous A/C operation during hot days
• Stop-start driving in summer traffic
• Older or poorly maintained air conditioning systems.

For commercial drivers and fleets, this can noticeably affect operating costs over the summer months. Occasionally, drivers miscalculate their fuel consumption in rural areas and run out, or end up paying highly inflated prices in back-country petrol stations.

Engine Cooling System Stress

Hot weather places sustained pressure on a vehicle’s cooling system. Radiators, coolant, hoses, and fans must work harder to maintain safe operating temperatures—especially when towing, climbing hills, or driving at low speeds.

Common summer-related issues include:

• Coolant leaks becoming more noticeable
• Overheating in traffic or slow-moving conditions
• Cooling fans running constantly

Vehicles that cope well in spring may struggle once peak summer temperatures arrive.

Tyres and Hot Road Surfaces

Road surfaces in New Zealand can reach very high temperatures during summer. This causes tyre pressures to rise, which can affect grip and accelerate wear.

Tyre-related risks in hot weather include:

• Increased likelihood of tyre failure or blowouts
• Reduced braking effectiveness
• Faster tread wear, especially on long trips

Checking tyre pressures regularly is particularly important during summer driving.

Driver Fatigue in Hot Conditions

Heat affects drivers as well as vehicles. Hot cabins, glare from strong sunlight, and dehydration can all reduce concentration and reaction times.

Long summer drives, such as holiday travel or rural work routes, can increase fatigue risk if drivers don’t take regular breaks or stay properly hydrated.

Practical Tips for Hot Weather Driving in New Zealand

Drivers can reduce summer driving risks by taking a few simple precautions:

• Slow down on shiny or sticky road surfaces
• Avoid parking on dry grass or vegetation
• Keep cooling systems serviced and coolant levels correct
• Check tyre pressures more frequently in hot weather
• Expect higher fuel consumption when using air conditioning
• Stay hydrated and take regular breaks on long journeys