Sick of the stifling stickiness? Here's how it happens.

Why do we feel mugginess?

When subtropical air masses arrive over New Zealand - especially in the north - they pack enough moisture to drive humidity levels up.

Aucklanders awoke to near 100 per cent humidity on Monday, but a better measure of that sticky mugginess we feel is called the dew point.

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That's the temperature at which, if cooled, water vapour from the air would condense on to a surface such as grass.

This required 100 per cent relative humidity and occurred when the air temperature equalled the dew point.

We really began feeling clammy when the air was both warm enough to make us sweat - but carried enough water vapour to interfere with that process.

So how does that work?

When temperatures rise, humans shed heat through the evaporation of sweat from our skin, which occurs smoothly when there's little moisture in the air.

But humidity compromised our ability to do so - which was why being in a rainforest was much more stressful on our physiology than a desert would be.

Because our sweat is essentially filtered blood - and it's the plasma of our blood that leaves through our sweat ducts - our bodies lose fluid that could have been used elsewhere, which leaves us feeling sapped of strength and energy.

Our bodies could adapt after just a few weeks of humid weather, by better balancing our fluids and sweating more efficiently.

But until that occurred, we found it harder to deal with mugginess than we otherwise might with dry heat.

If you were wondering why our hair turns frizzy when things get sticky, this was caused by extra amounts of hydrogen hanging in the air, which formed bonds between the protein and water molecules in hair, making it curlier.

What's the best relief?

Obviously, drinking lots of water - especially during exercise - helps us replenish that lost fluid.

And being somewhere with good air conditioning could help escape the clamminess.

In homes without air conditioning, getting to sleep could prove a struggle: but we could trick our bodies into sleepiness by taking a cooler shower about 30 minutes before bed.