Asthma sufferers could be facing a "perfect storm" of volatile weather conditions and high pollen levels.
The recent warm weather and on-going high pollen count has provided the perfect atmosphere for "thunder fever"- also known as "thunderstorm asthma".
As the Met Office issues another yellow warning for thunder , millions of asthma and hay fever sufferers have been warned that the impending storms could result in severe and potentially fatal symptoms.
This is due to a combination of stormy weather and sky-high pollen levels, which could trigger a dramatic rise in the number of dangerous asthma attacks, North Wales Live reports .
A specific blend of conditions must be met to give rise to the symptoms: high pollen count in the air, humidity and a northerly wind.
These conditions during stormy weather can generate massive amounts of microscopic pollen grains in the air which absorb moisture before exploding into tiny particles.
Winds then scatter the fine particles where they can easily be inhaled deep into the lungs, causing inflammation and irritation.
And for asthma sufferers, this can trigger an attack.
In 2017, 8500 people were hospitalised and nine died from asthma attacks after thunderstorms according to the Herald Sun .
The pollen count is expected to remain at very high levels until at least Friday, making it a difficult few days for sufferers.
Sonia Munde of Asthma UK said an estimated 3.3million Brits had their asthma triggered by pollen: "Thunderstorms can have a devastating impact on people with asthma and trigger an asthma attack which could be fatal.
"Humid, stormy conditions break the pollen into much smaller particles, which are then inhaled more deeply into the lungs and can lead to life-threatening asthma attacks."
People are advised to keep their medication to hand in the event of symptoms being triggered.
The changing conditions could also affect those struggling with hay fever.
Those with hay fever suffer an allergic reaction to pollen that usually gets worse between late March and September, when conditions are warm and humid.
It's estimated that 40% of the population suffer from hay fever, and even with closed windows, pollen can find its way indoors and prevent people from going about their day-to-day life.
