The NSW Government says "100 per cent" of the state is now in drought.
Figures from the Department of Primary Industries (DPI) show every part of the state is affected by the dry conditions, with almost one quarter classified as being in "intense drought".
Until now, some parts of the NSW north coast have either been classified as being not in, or recovering from, drought.
The State Government has already announced more than $1 billion in drought relief measures.
"We've seen the area of drought just expand slightly, we've seen the area of intense drought expand and slightly change its focus," DPI agricultural climatologist Anthony Clark said.
Less than 10 millimetres of rain has been recorded during the past month in the western, north west and central areas of NSW.
This map shows how Australia's big dry is affecting different parts of NSW.
Red areas are in "intense drought", orange areas are in "drought" and all other areas are "drought affected".
The DPI says the data shows parts of the central west recorded their driest July, and a lot of NSW experienced its driest autumn.
"This is tough, there isn't a person in the state that isn't hoping to see some rain for our farmers and regional communities," NSW Primary Industries Minister Niall Blair said.
"Producers are now faced with some very difficult decisions on whether to graze sown crops or rely on potential rainfall in the next two months in order to increase yield production."
Mr Clark said the outlook remained bleak for much of NSW.
"The probability of these warm, dry conditions continuing is a little higher," he said.
Chair of the Australian Fodder Industry Association Frank McRae said NSW had practically run out of feed for its animals.
"There's pretty much virtually nothing in NSW and supplies are rapidly drying up in southern Victoria," Mr McRae said.
"You have to go back to 1981-1982 to see a drought this widespread and so severe."
BOM meteorologist Jane Golding said every part of NSW normally received rain throughout June, July and August.
"This year we haven't really seen either of those and last year as well we didn't really see too much of the either of those rain bearing systems making their way into NSW," she said.
"It is unusually dry and also unusually warm which exacerbates the problems, so the warm temperatures dry out the soils even more."
The BOM and DPI said eastern Australia remained on an El Nino watch, which would reduce the likelihood of significant rains during spring.ABC