By Jessica McSweeney
If you were feeling extra hot and sweaty in Sydney on Thursday morning despite the temperatures barely touching 30 degrees, don’t fear – there’s a record-breaking reason why.
The hourly dew point observation in Sydney, the best indicator of how muggy the day is, reached the highest on record.
Warm water off the NSW coast contributed to the record dew point.Credit: IMOS OceanCurrent
By 11am at Sydney’s Observatory Hill, the dew point reached 25.9 degrees and at points surpassed 26 degrees, well above the January average of 14.9 degrees and just tipping over the previous record of 25.9 degrees on November 14, 2011, according to Weatherzone.
Once the dew point reaches above 24 degrees, the Bureau of Meteorology considers it to be at oppressive levels and warns the high level can contribute to possible heat stress.
Weatherzone meteorologist Ben Domensino said the high dew point was unusual for Sydney and more aligned with observations typical of Darwin.
“We’ve got very warm sea surface temperatures sitting off the coast of NSW that are warmer than average for this time of year. That warm water is causing more evaporation … which is bringing more moisture-filled air to Sydney,” he said.
Dew point temperatures are the best way to see how sweaty you’ll be as it tells the temperature at which the air must cool for condensation to occur.
The dew point is a direct measure of how much water vapour saturates the surrounding air. If you feel like the air is so thick and humid you could cut it with a knife, the dew point tells us why.
Humid days make it harder for sweat to evaporate into the air because it’s already thick with water vapour. This means you may feel much hotter than the actual recorded temperature.
In the city on Thursday the temperature hit 29.4 degrees at midday, however, the “feels like” temperature, according to the weather bureau, was 33.9 degrees.
In Penrith, the dew point hit 26.4 degrees at 10.30am, with a real temperature of 26.7 but a “feels like” temperature of 32.7.
Domensino said while the Observatory Hill weather station being moved to a grassier location in 2017 may contribute to higher readings, it doesn’t discount just how extreme the dew point reached on Thursday.
Senior Meteorologist at the Bureau of Meteorology, Stephen Stefanac, said there is unlikely to be any relief from the humid weather over the next few days.
Stefanac said humid, muggy days and nights are to come until Sunday, when milder weather is predicted to cool Sydney down.
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