As a result, the local population has been advised to "be prepared and store water" by the department.
"El Nino means extreme below normal rainfall for Vanuatu," VMGD's principal scientific officer Glenda Pakoa said.
"That means we might expect drier conditions for the next few months, and drier conditions can lead to water shortages and food shortages," she said.
"I would like to advise communities to make use of our wet season, store water, do not play around with water, especially farmers who plant crops that are resistant to drought events."
Pakoa said the islands in islands lay from north to south and so it would be normal for the Southern islands to face the impacts of the El Nino first, before the impact slowly progresses up into Northern islands.
"So, for the southern islands, it may take up to a few months. And then for the northern islands, it may take up to a year before we start to face impacts. This is how El Nino affects Vanuatu in the local context," she said.
The office began an El Nino watch in March of this year. In June, it moved to alert and in September it declared that El Nino conditions were fully established in Vanuatu.
The last El Nino event in Vanuatu, in 2015, caused extreme drought in parts of the country and food shortages.
"During that time, we had severe impacts of below-normal rainfall throughout the country," Pakoa said.
She said when the event occured in 2015 "communities had complained about their crops failing to yield sufficient food".
"We also have in terms of health we have diarrhoea, especially in areas where we find water shortages because when there is not enough water, we have water contamination in areas where people tend to look for sources of water in streams which is not healthy for communities.
So, with this El Nino event, we are more likely to expect similar impacts for our communities."
The cyclone season in the Pacific begins in November and runs until April 30 each year.
The VMGD will present the seasonal outlook statement for the upcoming Vanuatu 2023-2024 tropical cyclone season in October.
According to previous studies, El Nino does not really have an effect on the cyclone season, Pakoa said.
She also said that locals should make good use of passing tropical lows, especially during the cyclone season, to collect and store rainwater - in preparation for the dry season to come.
"I would like to advise everyone to prepare for the El Nino impacts that will still slowly but will still reach us in the coming months, and to stay up to date with relevant information from the VMGD," Pakoa said.