Parts of the Blue Mountains in NSW are having their wettest start to a year in 44 years.

As of 9am on Monday, Katoomba had received 920.1mm of rain since the beginning of 2020. This is the site's highest running total to this point in the year since 1976 and their sixth highest on record, with data available back to 1886.

Elsewhere in the mountains, Mount Boyce's year-to-date total of 741mm is its highest in records dating back to 1995, while Faulconbridge's 780.8mm beats records going back to at least 1986.

The bulk of this year's rain fell during February as a deep and slow-moving low pressure trough caused widespread rain in eastern NSW. Katoomba's 701mm during the month was its highest for February total since 1956. It was also the site's fourth highest monthly total on record for any time of the year.

Impressively, parts of the Blue Mountains have already seen more rain this year than they did throughout all of 2019. Mount Boyce's 741mm for the year-to-date trumps last year's annual total of 710mm.

Image: New growth in recently burnt bushland around the Blue Mountains. Photo: Blackheath Weather

This has been a pronounced turnaround from the exceptionally hot and dry weather that caused destructive bushfires in the Blue Mountains at the end of 2019.