Feeling beat by the heat?
Summer's sudden fast-forward to February conditions may have affected our brain and bodies in more ways than we might realise.
A string of La Nina-driven high pressure systems over New Zealand has plunged the country into a typically mid-summer climate with dramatic speed — especially when compared with this time last year.
"You're talking about a complete reversal, a flip of the script," Niwa meteorologist Ben Noll said.
The sudden change that hit in mid-November put last month's temperature 1.1C above average.
Dr Nicholas Gant, an expert on thermoregulation, said the change likely would have caught our biochemistry off-guard.
"What we are seeing in Auckland is February-like conditions very early on, and our bodies haven't had time to adapt to that," said Gant, the director of the University of Auckland's Exercise Neurometabolism Laboratory.
The temperature change could have wide-ranging effects on our body's normal biological cycle, or biorhythm, with implications for our mental, physical and emotional state.
Biorhythms rapidly disturbed by higher body temperatures could alter sleep quality and stress levels, and the demand of higher sweat rates and oxygen to shed heat energy, results in uncomfortable clamminess and losses of fluid.
"The worst examples of this are seen in athletes when they go and compete overseas in extreme climates where they have circulatory failures, because the body is shocked by the challenge," he said.
"We are seeing that to a lesser degree here."
People who worked outdoors or are required to wear stuffy uniforms might be noticing the change on their bodies more, especially if they aren't compensating with extra fluid intake.
Compounding the problem is the fact homes in the North Island generally have poor insulation, which makes them cold in winter, and too hot in summer.
"My recommendation would be that people strip down their bedding and nightwear as soon as they can to match it, get rid of the oil heater and drag in the fan."
Sleep researcher Dr Karyn O'Keeffe, of Massey University's Sleep Wake Research Centre, said we slumber best in ambient temperatures of between 13C and 23C.
But first we needed to cool our core body temperatures enough to doze off.
For those who didn't have air conditioning, opening a window or turning on a fan were obvious options.
Another science-backed tip was taking a cooler shower about 30 minutes before bed.
"The process of heating up and then cooling down afterwards can mimic the drop in body temperature that we experience as we get sleepy in the evening and eventually drop off to sleep," she said.
"A brief shower can therefore help with the process of sleepiness and sleep onset."
Trying to get to sleep two hours earlier than normal could be virtually impossible, as it went against the drive of our circadian body clock, and only left us feeling more frustrated.
And if the heat roused us awake in the middle of the night, one of the worst things we could do was reach for our tablets or smartphones to check the time.
"The strongest source of information for our (body) clocks is light, so when we bring it into a time or environment we're not expecting, we can push our clocks back later.
"But if we're just waking up in the dark and then trying to fall back to sleep, that's not enough to change it."
Constant disruption to sleep could dog normal cognitive processes, slowing our reaction time, cloud decision-making, impede communication and make us more irritable and moody.
"We also know the hormones that regulate our appetite and feeling of fullness changes quite rapidly with only a couple of nights of short sleep, meaning we tend to eat more because we don't feel full as easily."
While it might feel like the last thing any of us want to do at the moment, Gant suggested getting out for a run could help us swing into summer.
"Exercise in the heat, when not overdone, can help stimulate the adaptation your body needs to lose that heat quicker."