I have tried to pick the common weather conditions that prevail in Sydney and list the dive sites that could be suitable in those conditions.

GENERAL ADVICE

Open Ocean

My experience is that any winds over 15 knots from all but the west or north-west are unsuitable for boat diving. For 10 to 15 knots a lot of caution is needed. Any on-shore winds over 10 knots would also make most shore diving in the open ocean unsafe.

Harbour and Bays

Shiprock, Lilli Pilli, Camp Cove, Parsley Bay and Clifton Gardens are normally suitable for diving in all weather conditions (subject to tidal limitations at Shiprock) and are about the only places worth trying when the weather is bad.

Waves and Wave Periods

Swell direction and height is not the only thing that affects dive sites. The swell period can have even a bigger impact on dive sites than the height. For example, you can have a very small swell of under a metre which can make it extremely uncomfortable to dive at a site. Simply, the longer the period of the wave (that is, the time between the peak of each swell), the deeper the impact of the wave. The longer the period, the deeper the effect is felt and the worse it is felt if you are shallower.

In addition, longer the period, the more a swell can wrap around a headland. Even if a swell is from the south, it can, given long enough period, wrap around somewhere like Bluefish Point and Shelly Beach Headland and go right into the bay and cause waves on Shelly Beach (which faces the north). The same thing can happen to a greater extent at the Kurnell dive sites.

Click here to read a very detailed description about wave periods and how it affects scuba diving..

RAIN

Open Ocean

Generally, rain does not affect the visibility in the open ocean unless a huge amount, close to a flood, occurs. Even 100 mm of rain will not affect ocean dives. In 2022 Sydney had an enormous amount of rain which flooded all the rivers numerous times. The first flood in February and March for three weeks had over 450 mm fall. The first dive I did after this was at Middle Ground and I had one metre visibility on the bottom. Dives later in the year had very dirty water on top but cleaner underneath.

In short, unless the rivers are in flood, rain will not affect visibility on an ocean dive.

Harbour and Bays

No amount of rain falling overnight or the day before will affect visibility to such a degree that it is not worth diving. Even 50 or 75 mm will not do it, as this rain will be falling in the city proper and as it is coming off houses and street, there will not be a huge amount of dirt with it.

However, if more than 100 mm of rain has fallen in the past four days, then you will certainly get poor visibility in Port Hacking and possibly Botany Bay. Botany Bay may take longer to be affected, depending on the tides. Sydney Harbour will need more rain and a longer timeframe to be affected bad enough to not dive.

Apart from this limiting factor, sites like Clifton Gardens, Shiprock, Fairlight, Parsley Bay and Camp Cove (mostly) are always suitable and not included in later comments. Botany Bay sites are more open to the ocean so can be affected by weather conditions as below.

SOUTHERLY WINDS AND SEAS (includes SE and SW)

10 to 15 knots - 2 to 3 metres
Shore Dives
The open ocean would be undiveable except at Shelly Beach, Fairy Bower and South Maroubra. Inside the bays you could probably dive at Bare Island Right, Inscription Point, The Monuments and possibly Oak Park.

Boat Dives
Middle Ground, Six Fathom Reef, Pizza Reef, Barrens Hut out of Port Hacking, Inscription Point, Anchor Reef, GT Reef, Henry Head out of Botany Bay, The Gap, The Colours, Red Indian Point, South Head, SS Royal Shepherd out of Sydney Harbour would probably be okay. The SS Annie M. Miller could also be possible, but extreme care should be taken.

You could also probably dive inside Henry Head in Botany Bay.

Do not run north as you may have a lot of trouble getting back if the winds and seas get worse.

15 to 20 knots - 3 to 5 metres
Shore Dives
The open ocean would be undiveable except at Shelly Beach, Fairy Bower, and The Monuments, although even this last site may be not safe

Boat Dives
Only Six Fathom Reef at Port Hacking and perhaps Inscription Point out of Botany Bay and Red Indian Point in Sydney Harbour. You could also try The Container Wall in Botany Bay and Inside South Head and Sow and Pigs in Sydney Harbour.

Over 20 knots - 4 to 7 metres
Stay in bed.

NORTH EASTERLY AND EASTERLY WINDS

5 to 10 knots - 1 to 2 metres
Shore Dives
Bare Island is suitable for all strengths of NE and E winds as is Bass and Flinders. The open ocean would be marginal in many places. You could possibly dive Fairy Bower (E okay), Shelly Beach should be okay, Oak Park would probably also be okay as would Inscription Point. The Monuments would be good, especially in E winds. The Voodoo shore dive (not the dive I cover in this site) would be starting to become diveable.

Boat Dives
Most locations would be okay but you would not want to run into the NE for too long. If there is a NE wind when heading out and it is forecast to get stronger, if you must go a reasonable distance, head NE into the wind so that if it gets stronger, you will be running back with it.

15 to 20 knots - 3 to 5 metres
Shore Dives
Bare Island and Bass and Flinders would still be okay. The open ocean would be very unsafe. You could probably not dive Fairy Bower (E marginal) but Shelly Beach should be still okay. Oak Park is probably not okay. Inscription Point and the Monuments would probably not be diveable (but E winds may be okay). The Voodoo shore dive should now be possible.

Boat Dives
North Head would be a good place to dive as would inside North Head. In E winds, it would be rough here but you could still probably dive here. The entrance to Botany Bay would also be okay on the north side, with Henry Head (including inside) good and Minmi Trench a bit rough but diveable, although Minmi would be bad in E winds. Out of Port Hacking, Six Fathom Reef would probably be the only place to dive, although it would be very choppy.

Over 20 knots - 4 to 7 metres
Stay in bed except for Bare Island, Voodoo shore dive, Bass and Flinders and all the harbour dives.

NORTH WESTERLY OR WESTERLY WINDS

5 to 10 knots - 0.5 to 1 metres
Shore Dives
Westerly and north-westerly winds tend to flatten out the seas dramatically. However, it may take a day or more to cut the swell right down if it has be running at over 2 metres. Assuming that the wind has been running for more than a day, you should be able to dive most locations, although very hard places like Shark Point and Mahon Pool may still be a bit too rough.

Boat Dives
You should be able to dive all locations except perhaps ones right close to the rock platform.

10 to 15 knots - 0 to 0.5 metres
Shore Dives
Most places should be okay, with Shark Point and Mahon Pool now diveable.

Boat Dives
You will need to stick within a few hundred metres of the shore for comfort, although wrecks like the SS Myola and the wrecks at Long Reef will be starting to get a little uncomfortable.

15 to 20 knots - 0 metres in close
Shore Dives
All locations should be okay, but it will probably be too rough to get in off the western side of Bare Island. This is the time to dive Shark Point and Mahon Pool.

Boat Dives
Perfect for diving in close to the rock platform, the seas should be absolutely flat. The further out reefs and most of the wrecks may still be diveable, but you will need to run along the shore and then out to these sites. It will be uncomfortable at these sites and it could be too rough.

Over 20 knots - 0 metres in close
Shore Dives
All locations should be perfect, but it will be too rough to get in off the western side of Bare Island. This is the time to dive Shark Point and Mahon Pool.

Boat Dives

Unless the site is close to the shore, do not head out as you may get blown to New Zealand when the anchor rope breaks or the anchor comes free (as it probably will). I would not consider diving places like the wrecks at Long Reef or the Myola, reefs at the entrance to Sydney Harbour or Botany Bay, the SS Tuggerah or SS Undola.

It may even be too uncomfortable to drive the boat across Botany Bay from the only accessible boat ramps and even Sydney Harbour and Port Hacking will be very rough in spots.

RESOURCES

There are a number of resources where you can check the weather and forecasts for Sydney. I have links to the best ones on my weather page. Click here to see it.