Gunnedah-based zone operational readiness officer, Josh Clarke, told Australian Community Media that crews were on stand-by because heavy rain had been predicted.

"SES has been preparing across the state since Monday. The weather system is moving quite fast, faster than initially anticipated. It's moving down the east coast of Australia quite quickly, starting at the Hunter Valley," he said.

"It has been quite a few years since we've seen rainfalls of any significance in any area of this state and over the last few weeks we've seen an increase in weather patterns and rain, which is welcome, but with that comes inherent risks that we need to be mindful of.

"While the rain is a celebratory event, we're asking people to celebrate from a nice, dry, safe location."

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Mr Clarke said caution was key to safety.

"Heavy rain leads to flash flooding, so take your time, have a look and stay away from flood waters," he said.

"We're encouraging people not to enter flood waters or fast-moving water at all ... it's putting lives at risk and those sent to help you.

"A fortnight ago we did have a flood rescue, which caught people off-guard quite quickly."

Mr Clarke said the widespread bushfires could also impact water flow.

"The runoff of water may contain ash because we have got a lot of burnt areas with bushfires. Loose ash will move into the water catchment and will cause changes in the flow of water. People are used to water moving in a certain way and it may change," he said.

Mr Clarke said the SES would keep people up-to-date across social media platforms.

"The big message is - celebrate the rains but from a safe and dry location. If you come across flash flooding, or need assistance from the SES, call 132 500 and if it's life-threatening call 000," he said.

Thunderstorms and rainfalls of up to 25mm are predicted for Tamworth and Gunnedah over the weekend and into next week.