Adelaide is a city of extremes. Honestly, anyone who has spent a January afternoon near North Terrace knows the feeling. It’s that dry, searing heat that feels like standing a bit too close to an open oven. Today, Sunday, January 18, 2026, we’re right in the thick of it. The current temperature has hit a staggering 99°F (around 37.2°C), and with a humidity level of just 15%, it is basically as dry as a bone out there.
If you're out and about, you've probably noticed that the wind is coming from the north at a gentle 4 mph. That's the problem. Those northerly winds are notorious for dragging the hot air from the Red Centre straight down into the Adelaide plains. It's a classic South Australian summer setup. But here is the thing: the weather forecast Adelaide SA shows a massive shift coming within the next 24 hours.
What’s Actually Happening with the Adelaide Weather Right Now?
It's partly sunny today, but don't let those few clouds fool you into thinking it's cooling down. The UV index is currently sitting at a 3, but the daily peak is much higher—reaching a UV index of 10. That’s "very high" territory. If you’re heading to Glenelg or Henley Beach, the sun will bite before you even realize you’re burning.
The low humidity is a double-edged sword. It means you don't get that sticky, muggy feeling you’d find in Brisbane, but it also means your body dehydrates way faster. You might not even feel sweaty because the moisture evaporates off your skin instantly.
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The Week Ahead: A Rollercoaster of Temps
The "blast furnace" isn't staying forever. In fact, Monday brings a significant "cool" change. Here is what the rest of the week looks like:
- Monday, January 19: A sharp drop to 85°F. The wind flips to the southwest at 14 mph, bringing that delicious Southern Ocean air.
- Tuesday, January 20: The cooling continues. Expect a high of 82°F and a jump in humidity to 51%. It'll feel like a different city.
- Wednesday, January 21: Mostly sunny and 84°F. Perfect "beer garden" weather.
- Thursday, January 22: Back down to 82°F with clear skies.
Basically, if you can survive the 99°F heat of today, you’ve got a very pleasant run of low-80s weather coming your way.
The Mediterranean Mystery
Adelaide is often cited by experts like those at Tourism Australia as having a Mediterranean climate. But what does that actually mean for your weekend plans? It means our rainfall is unreliable in summer. For today, there is only a tiny 4% chance of rain. Even as we move into Tuesday, where the chance of rain "spikes" to 20%, we are talking about light, fleeting showers rather than a washout.
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The real danger in Adelaide isn't the rain; it's the lack of it combined with those north winds. When the temperature hits the high 30s or low 40s (Celsius), the fire danger ratings usually climb to "High" or "Extreme" in the Adelaide Hills. Currently, for today, the winds are light, but by Tuesday, we’re looking at southerly gusts up to 18 mph.
Why the Night-time Low Matters
Tonight, the temperature is only dropping to 69°F. In a stone or brick house, that heat gets trapped. Without a decent sea breeze, the "apparent temperature" inside remains high, making it hard to sleep. Tomorrow night (Monday) will be much more manageable at 61°F.
Actionable Tips for the Next 48 Hours
If you’re living through this current spike, here is the expert-level advice that locals swear by.
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- The Blinds Rule: Close every single blind and curtain on the northern and western sides of your house before 9:00 AM. Once the sun hits the glass, it's too late; the greenhouse effect is already working against you.
- Hydrate Beyond Thirst: Because the humidity is only 15%, you are losing water through respiration and skin evaporation constantly. If you feel thirsty, you're already behind the curve.
- Check the UV Window: The Bureau of Meteorology often highlights the "sun protection times." With a UV index of 10 today, that window is basically from 10:00 AM to 5:00 PM.
- Watch the Wind: Keep an eye on the wind direction. As soon as it swings from North to Southwest (expected tomorrow), open the house up. That’s your free air conditioning.
The heat today is intense, but the weather forecast Adelaide SA confirms it's a short-lived peak. By Tuesday, the temperature will have dropped by 17 degrees, making it the perfect time for a stroll through the Botanic Gardens or a trip up to the Adelaide Hills where it'll be even cooler.
Stay cool, keep the water bottle full, and just remember: Monday is coming.