The thermometers are due to register 46.7C in Córdoba, 45.6C in Seville, 44.8C in Badajoz, and 44.7C in Mérida and a record 46.9C in Jaen.
The provinces of Jaén, Córdoba, Granada and Sevilla in Andalusia, and Cáceres and Badajoz in Extremadura have been issued with red warnings (indictaing extreme risk) by Spain's state meteorological agency (AEMET).
A further 21 provinces across Spain are on amber or yellow alert for high temperatures (risk or high risk), which increase the risk of wildfires.
Temperatures are predicted to reach record highs on Thursday before cooling at the weekend.
Here's The Local top tips for staying safe during hot weather.
Protect against sunburn
Cover up or apply cream Photo: AFP
Not only is a brighter shade of lobster deeply unattractive and likely to increase your chance of skin cancer but sunburn can greatly contribute to heatstroke. Stay in the shade, protect yourself with a wide-brimmed hat and apply high factor sun cream.
Never sit in a parked car
It's amazing how quickly a parked car can turn into an oven in the Spanish sun, even in just a few minutes. Never leave anyone, and that includes dogs, in a parked car, even if the windows are open a crack and the car is in the shade.
A worker takes a snooze in Seville. Photo: Karolina Lubryczynska
There is a reason why Spain traditionally comes to a standstill on summer afternoons. Avoid strenuous activity and find a cool spot to rest during the hottest hours of the day. If you can, we recommend a siesta.
Wear loosefitting and lightweight clothing
To allow air to circulate around your skin and let your body cool properly avoid tight clothes and synthetic fibres.
Whether it's taking a dip in the nearest swimming pool, sheltering in an air-conditioned shopping mall or lying low in a darkened apartment, there are always sanctuaries at hand to escape the heat.
Get used to it
Don't overdo it in the heat until you become acclimatized. Locals may deal with the summer temperatures better than visitors so allow yourself some weeks to adjust and accept that some people from colder climes never do.
Drink plenty of fluids
Unfortunately that doesn't mean sangria or cerveza. Staying hydrated will help your body sweat to maintain a normal body temperature, so always have a bottle of water at hand.
Age, medical conditions and fitness levels can all have an impact on how you deal with the heat. And remember that certain medications or medical conditions can increase the risk of heat-related problems.
If you feel really ill, seek medical advice.