Christchurch is forecast to reach 29C while Masterton will reach 27C.<\/p>\n
Both Auckland and Hamilton are forecast to reach 25C while Gisborne and Napier will reach 26C and 27C respectively. <\/p>\n
Law said temperatures were nearing the threshold for MetService to issue a heat alert.<\/p>\n
\u201cIt\u2019s the combination of the hot days and the warm muggy nights which is the more concerning figure,\u201d Law remarked.<\/p>\n
MetService will issue an online heat alert when temperatures across the country pass certain thresholds, the top 1% of temperatures. <\/p>\n
Other aspects, such as high humidity, are taken into account before issuing the alert. <\/p>\n
Law said they would ideally only be triggered once or twice a year. <\/p>\n
\u201cWhat we have coming up is not that each day is going to be exceptionally hot; it\u2019s the combination of high temperatures during the day and really warm overnight.<\/p>\n
\u201cIt\u2019s that average temperature which could trigger that heat alert for places like Canterbury.\u201d<\/p>\n
According to MetService, Auckland\u2019s overnight temperature would be 18C tonight and Wednesday.<\/p>\n
The forecaster attributed the high temperatures to warm air being dragged down from the tropics towards New Zealand.<\/p>\n
\u201cThe warmer the air, it tends to have more moisture which adds to the muggy conditions,\u201d he said.<\/p>\n
\u201cWe won\u2019t lose the heat of the day and we\u2019ll keep the muggy nights as well.\u201d<\/p>\n
MetService has issued two heavy rain watches for the South Island\u2019s west coast from overnight until late tomorrow morning. <\/p>\n
Law said windy conditions would plague Buller and Canterbury.<\/p>\n
In the North Island, warm air in the Hawke\u2019s Bay could be enough to bring in rain.<\/p>\n
\u201cPerhaps some heavy showers, some heavy rumbles of thunder and even some hail through the afternoon,\u201d Law said.<\/p>\n