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What is "normal”? It is one of those age-old questions that sounds simple to answer but has you scratching your head and struggling to explain it.

Even if you can elucidate on what it is, is "normal” a good thing? Do I even want to be "normal”, and cast off any elements of individuality just to be part of one huge, boring, homogenous crowd? Or is being normal, or thereabouts, something we should all aspire to, given humans are social animals?

Certainly some of what goes on around the world in defence of "normal”, or of what is said to be the "normal thing to do”, is morally questionable and at odds with what many reasonable-minded people feel comfortable with.

There is no doubt, though, that whatever normal is, it can change over the years. What many might hardly bat an eyelid at now might have been cause for uproar and scandalised shrieking decades or centuries ago.

So as society becomes, supposedly, more tolerant and accepting of what some might have once considered not normal, the baseline for the normal — or the average, standard, ordinary or whatever you want to call it — changes.

And so it is with the way we are measuring our changing climate, specifically our measures of temperature and rainfall normals.

Niwa science staff have embarked on an at least six-month mission to update those climate normals to incorporate the latest decade of readings from around New Zealand. That follows a decree from the World Meteorological Organisation, which says the 30-year period is the accepted statistical one against which to measure changing climate.

Our current climate normals have been the 30-year average of rainfall and temperature readings taken between 1981 and 2010. When climatologists talk about a certain month’s temperatures as being "above normal”, they are comparing that month with the average temperature for that month over those three decades.

The new normals will cover 1991 to 2020. It will come as a surprise to no-one that the baseline temperatures will be higher than in the previous 30-year period and, as a result, monthly averages may not appear as elevated as in the past.

One of the incentives to change the baseline is so that frequent and increasingly warm months do not merely become white noise and get met with a shrug of the shoulders. A reset higher temperature baseline will make the warmest months look less extreme — as they are part of a warming climate — and instead show more clearly any colder-than-average months.

We have to go all the way back to January 2017 to find New Zealand’s last colder-than-normal month relative to the 1981-2010 average. In contrast, last month was the warmest June in at least 110 years, with average temperatures 2 degrees Celsius above all the other Junes in that three-decade period.

The mind is a strange and complicated place and the memory is fickle. While it might seem like June was cold in the South, in reality it was only the last few days of the month that were.

Another benefit of moving to a 1991-2020 baseline is that we are able to more easily compare temperatures and rainfall to other times we have lived through and experienced. The climate has changed considerably during the past few generations, and a winter that great-grandparents may have thought warm in their day probably will not feel that unusual to their great-grandchildren today.

Humans are competitive creatures. Like Mrs Bucket in Keeping Up Appearances, we constantly need to compare, and contrast, to make sense of things and our place in the world, whether it be the quality of the neighbour’s curtains, the strength of our national sports teams, or how hot, or cold, this month has been compared with last year and beyond.

When it comes to weather and climate, it is crucial to have the most accurate and robust data. It is from that that important policy decisions which affect our future can be made.