“Lord Howe Island has a subtropical maritime climate.”
The seasons change gradually: winters are cool and wet with even rainfall; summers are warm and mild with fairly high but less regular falls of rain. Daily maximum temperatures average around 25°C in the summer months to 18°C during winter. The minimum average temperatures are 19°C to 13°C over the same period.
Relative humidity varies little year-round, generally being in the high sixties to seventies. January and February can have tropical air around the island with more humid days in the 80 to 90 percent range. The fact that Lord Howe Island is surrounded by the moderating effects of the ocean ensures the continuation of this moist, humid climate with its small daily and annual range in temperature and humidity.
Rainfall is seasonal, with about 180 mm in June and July, and 120 mm in the summer months. Most rainfall occurs as moderate to heavy showers and not continuous rain, but winter frontal systems can bring rain bands that may last for a day or more. The summers are actually drier than the statistics indicate, because some years bring erratic tropical lows that can boost the average figures by up to 300mm in a month, other years 5mm a month may occur.
Winds are generally west to southwest in winter, and east to southeast in summer months. The island is too far south to experience cyclones, but remnant cyclones that decrease to tropical lows can pass over the island and bring strong winds. Each winter several episodes of gale force winds (over 33 knots) can affect the island as east coast lows move across the Tasman Sea.
Water temperatures around the Island vary from a low of 17°C in August to 25°C in March, although the lagoon can be warmer on sunny days. Generally, conditions are mild enough to enjoy swimming between the months of November and May.
The summer temperatures are getting higher, with daytime maximums over 28°C not uncommon now. These changes are impacting ecosystems on the island.