May 2019 was characterised by higher than normal sea level pressure over and to the east of the North Island and lower than normal pressure to the south of the South Island. This resulted in more northwesterly winds than usual over the country.
Temperature
The distinct lack of southerlies throughout the month, frequent rounds of high pressure and warmer than average seas contributed to unseasonably warm temperatures and what is now officially New Zealand’s 3rd warmest May on record. Temperatures were above average (0.51°C to 1.2°C above average) or well above average (>1.2°C above average) across the entire country, with the most unusually warm temperatures in the South Island. Many locations observed record or near-record warm mean, mean maximum, and mean minimum May temperatures.
Rainfall
Rainfall was below normal (50% to 79% of normal) or well below normal (<50% of normal) for the majority of the North Island, with the exception being parts of Waikato, Taranaki, and coastal Manawatu-Whanganui where rainfall was near normal (80% to 119% of normal). Rainfall was above (120% to 149% of normal) or well above (>149% of normal) normal for much of western and lower South Island. Near or below normal rainfall occurred in parts of Marlborough, Canterbury, coastal Otago, and southern Southland.
Soil Moisture
As of 31 May, soils were drier than normal for much of the North Island with small areas of wetter than normal soils about western Waitomo and the Kapiti Coast. South Island soil moisture was generally near normal with pockets of below normal soil moisture about Waimate and Waitaki as well as the interior Marlborough region.
