Brisbane 22.6C at 8.30am as spring heat builds

Sunny, light winds and 31 C in the city today.

The Brisbane automatic weather station clocked 22.6° at 8.30am on Friday 4 September, with a light south-westerly at 6 km/h and nothing in the rain gauge.

That reading matters because it is already sitting near where a typical Brisbane September afternoon lands, somewhere around the mid 20s.

The same station was on 15.0° at 6.00am in calm conditions, so the mercury lifted 7.6 degrees in two and a half hours.

The morning never really cooled off, and the heat of the day is now stacking on top of a start that was warm before most trailers reached the ramp.

Where the numbers sat at 8.30am

Amberley was on 21.8° at 8.30am with no rain recorded, so this was not just an inner-city concrete story.

Toowoomba, up on the range and usually the cool option for a weekend away, read 19.9° at the same time.

Rockhampton sat on 18.9° at 8.42am, which shows the warm air was banked up over the south-east rather than the whole coast.

The barometer at the Brisbane site was 1020.8 hPa, the sort of number that goes with a big fat high and very little to move the air around.

What is driving it

A large high pressure system has settled over the continent behind the run of southern fronts, and Queensland has copped the sunny, light-wind side of the deal.

James Pescott from the Bureau of Meteorology flagged the change on Monday 31 August.

"As we start spring, the temperatures will rise really from midweek as that high-pressure system weakens and we have a weak trough system move across southern Queensland."

That is exactly how Friday has played out, with clear skies, barely a breeze and daytime heating doing its work uninterrupted.

Friday and the weekend

Today: the forecast has Brisbane at a maximum of 31° C on a minimum of 17°, sunny with light winds, UV very high at index 8 and fire danger Moderate.

Saturday: 30° with a low of 16° , mostly sunny, light winds becoming north to north-easterly at 15 to 20 km/h early afternoon then light in the evening.

Sunday: 35 C on 18° , mostly sunny with light winds again, which is a genuine step up for the first week of spring.

For early September, 31° is unseasonably hot, and Sunday's 35° is the kind of number most of us file under November.

What it means on the water

Moreton Bay will look glassy and inviting through Friday morning with that light south-westerly, and glassy plus 31° is how people get caught out.

The water is still carrying winter temperatures, so this is an air heat event rather than a warm swim.

That mismatch is worth respecting if you are kiting, foiling or paddling and planning a long session in a spring wetsuit.

A dunking will still pull heat out of you quickly, while the sun above is working hard in the other direction.

Ramps at Manly, Shorncliffe and Scarborough will be busy early, and the smart move is getting the boat wet before the UV peak.

Burn time: with the UV index forecast at 8, the burn window on unprotected skin is short, so a shirt, hat, zinc and polarised sunnies are not optional extras.

Boat decks, aluminium gunwales and vinyl seats get genuinely hot under a sunny 31° sky, so bare feet and small kids need watching.

Gold Coast beaches and the Broadwater will take whatever sea breeze turns up, and Saturday's early afternoon north-easterly at 15 to 20 km/h is the useful window for sailors.

Friday's light winds mean the wind-driven crowd is probably better off swimming, paddling or fishing than waiting on a breeze that is not coming.

Fire danger and the wider picture

Fire danger for Brisbane is rated Moderate on Friday, which is the low end of the scale but still worth a look if you are camping near the water.

Moderate means most fires can be controlled, though conditions can shift quickly once temperatures climb and humidity drops away in the afternoon.

Keep an eye on the Queensland Fire Department ratings if your weekend involves a beach camp, an island trip or a long tow through dry country.

How to play the weekend

Go early. Launch at first light, get the session done before 10am and be under shade by the time the UV peaks.

Water on board. Carry more than you think you need, because heat, glare and a day on the bay dehydrate people faster than they notice.

Check the breeze. Saturday afternoon's north-easterly is the only decent wind in the three-day window, so build any sailing plan around it.

Mind the kids and dogs. Hot decks and no shade on a small runabout add up quickly when the air is sitting on 31 C.

Sunday's 35° with light winds will feel heavier again, so anything strenuous on the water becomes a dawn job.

You can keep tabs on official alerts through the Seabreeze Queensland warnings page before you hook up the trailer.

For breeze detail, the Brisbane wind forecast will show whether Saturday's north-easterly holds long enough for a run down the bay.