"I'm like a human barometer. I can tell when a storm is coming before I see clouds in the sky," said the 49-year-old.
"Sometimes it can be more mild and sometimes they can be so debilitating that I'm vomiting and I have to go to bed."
South first noticed a link between her attacks and humid, stormy weather some 20 years ago. When over-the-counter medication wasn't helping, she asked other migraine suffers about a potential link to environmental factors and realized there might be something to it.
After speaking to a specialist and developing a plan to cope with the attacks, South began trying to stave off her headaches before they took hold. She discovered that she was more susceptible to a weather-related headache if other factors were in play.
"If I'm tired or if I've had alcohol or sometimes chocolate in combination with the storm, the triggers work together to light the fuse that blows the dynamite off in my head," she said.
"I'm always watching the Weather Network and reading the paper and listening to the radio for storms coming in and then I try to be on my best behaviour with my other triggers."
South is now executive director of Headache Network Canada, a charitable organization that aims to educate sufferers and health professionals on all aspects of headache diagnosis and treatment. After years of dealing with her own headaches, South urges others who may be susceptible to similar attacks not to dismiss a potential connection between their pounding heads and the weather.
While the reason for the link between the weather and headaches of varying severity is still unclear, doctors now know that environmental factors play a big role.
"For a lot of headache sufferers they notice that seasonal change can be a time of worsening headaches for them," said Dr. Christine Lay, director of the Centre for Headache at Women’s College Hospital in Toronto. "Probably more than 50 per cent of migraine patients have some kind of weather trigger."
Studies have shown that a rise in temperature by a few degrees - no matter what the season - can trigger headache attacks, she said. Other weather features, including bright sunshine, humidity levels and shifts in barometric pressure are all also factors that play a role.
And while weather changes can have a distinct impact on those who know they suffer from migraine attacks in particular, Lay explained that even people who think they might have a simple tension headache ought to consider a link to the environment.
"The majority of migraine patients are undiagnosed," she said, adding that weather-triggered migraine attacks are often mischaracterized as sinus headaches or bad tension headaches.
To compound matters, summer activities such as enjoying barbecued meats containing nitrites - a known headache aggravator - and a tendency to opt for colourful summer cocktails carrying dyes and artificial sweeteners, can all make a person more vulnerable to a weather-related headache, said Lay.
"It's a combination of the weather change and sometimes what we do in the summer," she said. "The main thing is awareness, rather than discounting it. A lot of people will just say ‘oh it's just a weather headache.' It's best just not to ignore it but to really get advice from doctor."
Once people do see their physicians, one of the best ways to deal with weather-related headaches is to figure out just which kind of environmental feature brings on an individual's attack.
"What type of weather pattern changes trigger off one individual's headaches may not trigger off another individual's headaches. What we suggest is that individuals keep a headache diary," said Dr. Gary Shapero, a Markham, Ont.-based family physician and director of the Shapero Markham Headache and Pain Treatment Centre.
"What they need to do is educate themselves on what the potential triggers are and then try to identify what those triggers are for them."
Once those triggers have been identified, as the weather itself is out of their control, patients are urged to focus on avoiding the headache aggravators they do have power over, Shapero said. That could include ensuring proper sleep and meal patterns are followed.
If however, despite all attempts at avoidance, an attack is triggered by the weather, Shapero advises his patients to take their acute migraine medication for relief. More serious cases, involving patients who are extremely sensitive to their individual triggers, may be prescribed preventative headache medication taken daily over the long-term.
In addition to migraine-related episodes, cluster headaches, which are an entirely different kind of distinct headache, may also have links to the weather, said Shapero.
In those cases, he explained, patients often wake up in the middle of the night with an intense pain on one side of their head that lasts for an hour or two before disappearing. The headache may reappear once or twice in a day, every day, for two or three months before stopping entirely for several months.
"The episodes of cluster headaches can be triggered off by changes of season," said Shapero. "People will start that process of daily headaches during the spring and the fall, and when in the midst of that cluster period, they may find that heat and hot weather will trigger off a specific headache attack."
No matter what kind of headache experienced, the bottom line recommended by specialists is for people to investigate just what might be bringing on that pounding head.
"More awareness is important," said Shapero, who cautioned against a dependence on over-the-counter drugs as too many such doses could actually cause headaches to get worse over time.
"People really need to educate themselves. They need to get to their family physician, and get a proper diagnosis."