Summer's coming. Here's what's worth changing and what isn't.
What genuinely changes
You need more sunscreen, more often. Not a different sunscreen necessarily, just more of it and reapplied properly. Most people apply roughly a third of the amount the SPF rating was tested at, which turns an SPF 50 into something considerably less impressive.
Textures get lighter. A rich cream that suited July will feel like cling film in January. Switching to something lighter isn't vanity, it's the difference between wearing it and skipping it.
Storage matters more. A serum in a hot bathroom degrades faster. A sunscreen left in a car is effectively finished. Both are common and both are avoidable.
Reapplication becomes the whole game. Morning sunscreen does not last until evening, particularly if you've been swimming or sweating. A stick or a spray in the car or the bag is worth more than upgrading your serum.
What doesn't change
Your actives, mostly. Vitamin C works the same in January as in July. Retinol still goes on at night.
The idea that you need an entirely separate summer routine is largely a way to sell you a second set of everything.
The thing nobody mentions about air conditioning
An Australian summer is often spent indoors in dry, conditioned air, then briefly outdoors in intense heat, then back into the cold again. That cycling is harder on skin than either extreme on its own.
If your skin gets worse in summer despite doing everything right, the office air conditioning is a reasonable suspect.
The UV index number worth knowing
Sun protection is recommended whenever the UV index is 3 or above. In much of Australia that's most of the year, and in the far north it's essentially always.
The Bureau of Meteorology publishes it daily and most weather apps show it. It's a more useful number than the temperature, and almost nobody looks at it. Cool, overcast days in October will happily deliver a UV index of 8.
The short version
Lighter textures, far more sunscreen, better storage, and check the UV index rather than the thermometer. Everything else can stay as it is.
General information, not personal advice.