How do I keep food safe in hot weather?

Food poisoning peaks in summer for a simple reason: bacteria multiply faster the warmer it is, and everything about summer eating — picnics, barbecues, cars, long buffets — extends the time food spends warm.

Safety

Step by step

1. Halve the safe window.Two hours at ordinary room temperature becomes one hour above about 25°C. That single adjustment covers most summer food safety, and the time is cumulative across the day rather than resetting.
2. Do the chilled shopping last.Fridge and freezer items into the trolley at the end and into the car last. Then straight home — not via three other errands with shopping in a hot boot.
3. Use a cool bag every time in summer.Not only for long journeys. A car interior reaches well above outdoor temperature within minutes in sun, and a cool bag with a freezer block is the difference between chilled and warm on arrival.
4. Chill food thoroughly before it leaves the house.For a picnic or a party, everything goes out of the fridge cold, not room temperature. A cool bag maintains a temperature; it does not create one.
5. Keep the cool bag out of the sun.In the footwell rather than the boot, in the shade rather than on the grass. A cool bag in direct sun loses its margin quickly.
6. Put out half a buffet at a time.Half on the table, half in the fridge, replacing rather than topping up. Adding fresh food to a dish that has been out for three hours does not reset the clock on any of it.
7. Handle barbecues with separate everything.Separate plates and tongs for raw and cooked, and raw meat kept chilled until the moment it goes on. Cross-contamination at a barbecue is at least as common a cause of illness as undercooking.
8. Cook barbecue meat through and check it.Charred outside is not evidence of a cooked inside. 75°C in the thickest part for chicken, sausages, burgers and pork, checked with a thermometer rather than by colour.
9. Take particular care with high-risk foods.Cooked rice, cooked meat, dairy, egg-based dressings and desserts, seafood, and anything with a sauce. These have far less margin in heat than bread, hard cheese or whole fruit.
10. Keep the fridge closed and check the temperature.A fridge in a hot kitchen with the door opened constantly struggles to hold 5°C. A cheap fridge thermometer tells you whether yours is coping in a heatwave.
11. Cool leftovers fast and refrigerate them.Shallow containers, within an hour in hot weather rather than two. Food left to cool on a worktop in a warm kitchen is the classic summer mistake.
12. Rethink the food rather than the precautions.For a long hot day out, a picnic built on bread, hard cheese, cured meat, whole fruit and crisps carries almost no risk. That is a better answer than managing the risk of a chicken salad for six hours.
13. Discard rather than gamble.Anything that has been warm for an uncertain length of time. It cannot be judged by smell or appearance, and reheating does not fix it.

Tips

• Freeze drinks or a bottle of water and pack them with the food. They keep the bag cold and are drinkable later.
• A cool box with a fitted lid holds temperature far better than a soft bag for a whole day out.
• Bring perishable leftovers home in the cool bag rather than eating them later at the picnic. Once the ice packs have gone, the margin has too.

Common mistakes

• Topping up a buffet dish rather than replacing it — The food already on the table has been in the warm for hours. Adding fresh food to it does not reset anything and puts the new food into the same dish.
• Leaving shopping in a car while doing something else — A car interior in summer sun exceeds 25°C within minutes and can reach far higher. Chilled shopping goes home first.

If it doesn't work

Questions people ask