It said rain was expected to become heavy from around 2am Thursday morning in the west and 4am in the east. Between 130 to 160 millimetres of rain was expected to accumulate in the 15 - 18 hours following.
"While the situation in constantly changing, it has the potential to be a significant event and therefore residents are strongly urged to be aware and prepare accordingly.
"We suggest that you: check that any drains and gutters around your property are clear so the rain goes where it's supposed to; bring pets inside, move stock to shelter; drive with caution and if possible, avoid low-lying coastal roads; keep up-to-date with weather forecasts; check emergency food and water provisions," the statement said.
Weather was set to improve for the weekend, with fine spells and a few showers on Good Friday with a high of 23 C according to Mr Doolin.
Saturday was expected to fine but Mr Doolin warned there could be isolated showers and a high of 22 C.
Easter Sunday would be cloudy with the risk of showers.
"The weekend should be alright, there's the risk of showers but hopefully people can avoid those," Mr Doolin said.