Australia is at heightened risk of an above-average number of tropical cyclones until May, and also that they will develop earlier than usual.

Bureau of Meteorology (BOM) forecasts for October-April reveal increased risk of widespread flooding for eastern and northern Australia, and more tropical lows which can bring heavy rainfall over land or signal the early stages of tropical cyclone development if they pick up wind and speed at sea.

Tides are expected to be unusually high around January 23 on the NSW and southern Queensland coasts, and around February 20 on northern Queensland coasts, based on alignment of the earth, moon and sun orbits.

BOM says flooding is likely to occur in low-lying areas around these unusually high tides. More severe coastal flooding could occur if coastal or offshore storms are also present.

The warning comes after heavy rain saw the NSW State Emergency Service field more than a thousand calls for help over the weekend and respond to 44 flood rescues.

Rain has eased since but there are more than 100 flood and 16 emergency warnings across the state, and evacuation orders remain as dozens of rivers are still flooding.

October to April is the peak time in Australia for flooding, tropical cyclones, heatwaves, bushfires and severe thunderstorms. This season, there is greater than 70% chance of at least 11 tropical cyclones – the long-term average – as well as an elevated risk of grass fire and prolonged heatwaves in southern areas of Australia, with higher humidity.

“Communities are urged to prepare now as there is an increased chance that the first tropical cyclone in the Australian region is likely to be earlier in the season,” BOM said today.

Australia has had at least one tropical cyclone cross the coast every season since records began in the early 1970s. Normally, around four cross the coast each year. Coastal areas can be affected even when tropical cyclones stay offshore, especially during high tides.

“The impacts can include damaging or destructive winds, heavy rain leading to flooding, and other hazards such as trees being uprooted due to wet soils, landslips in steep areas and coastal erosion,” BOM said.

BOM is expecting widespread and prolonged riverine flooding across northern and eastern Australia, saying “rivers are high, dams are full, and catchments are wet across much of eastern Australia, meaning any rainfall has the potential to lead to widespread flooding”.

Above-average rainfall over winter has led to grass and vegetation growth in many areas, which can increase the risk of grass fires, and the wet 2022 spring could increase fire danger during any period of hot and dry weather over summer.

“Areas on the urban fringe next to grasslands may have an increased risk from grass fires,” BOM said.

In southern areas heatwaves may last longer, be warmer overnight and more humid, which can be a health risk. Heatwaves have caused more deaths than bushfires, floods, cyclones and severe storms combined.

Warmer sea temperatures for an extended timeframe could also affect fisheries and other marine life.