Four words to help you navigate daylight saving ending

Spring forward, fall back.

That simple mnemonic phrase is all you need to work out which way to turn your clocks when daylight saving ends this weekend – assuming you still have a device or two that requires changing manually.

In spring, turn your clocks forward an hour. In fall (or autumn as we Aussies call it), turn them back an hour.

READ MORE: Don't make this common daylight saving mistake

Daylight saving ends at 3am this coming Sunday in New South Wales, Victoria, the ACT, Tasmania, and South Australia, April 5. At that moment, it will become 2am.

The reversion to standard time across Australia means that from the early hours of Sunday, Perth will be two hours behind the eastern capitals, while Adelaide and Darwin will be half an hour behind – that is, until we do it all again in October.

How does the daylight saving changeover affect weather data?

One of the ways that the changeover affects weather data is in the 9am observations.

The BoM collates Australian weather data based on a 24-hour weather day from 9am to 9am. Some weather stations only record 9am and 3pm observations, while a few only record 9am data – usually because they are remote and/or manually operated.

But the 'old’ 9am effectively becomes an hour later when the daylight saving changeover occurs a few days into April, which means you’re not quite comparing apples with apples with 9am readings across the entire month.

Don't panic at 3am this Sunday. Just turn your clocks back an hour if your state has daylight saving
Image: Graph of air temperature in Melbourne on a day in March, showing a typical rapid rise between 8am and 9am (standard time). Source: BoM.

As the graph above shows, this time of day also happens to be when the mercury tends to rise most rapidly in many areas.

So the impact of comparing 9am temperature data across a month when 9am effectively means two different times is accentuated.

This is not a problem for maximum and minimum temperature data – as daily highs and lows can occur anytime within the 24-hour weather day.

But when you’re comparing data related to factors like temperature or humidity at a specific point in time, it can make for statistical headaches.

But that’s for the BoM to worry about. The rest of us just have our chocolate sugar rush headaches to concern ourselves with. We hope you have a good break this Easter if you’re lucky enough to be off work.