While conducting a local soaring flight to the north-east of Bacchus Marsh Aerodrome the pilot noticed rain approaching from the west on a broad front. He then noted that heavy rain was falling on the aerodrome but the area to the south-west of the aerodrome appeared to be clearing up. The pilot flew the aircraft towards the clear area and prepared to join the circuit for a landing on strip 27. The pilot reported that he encountered rain and heavy sink all the way back to the circuit area. He joined the circuit turning crosswind earlier than normal. Strong drift and sink were encountered so the pilot immediately turned onto final approach. He reported that when established on final approach at 75 knots the aircraft was not penetrating at all. It was then apparent that the aircraft was not going to get to the field. The pilot turned the aircraft left towards the south to avoid the aerodrome boundary fence but there were no paddocks ahead suitable for a landing. He kept the turn going until the aircraft was heading in an easterly direction away from the aerodrome to make a downwind landing. When he released the airbrakes the aircraft immediately descended rapidly. The pilot said that he could not arrest the descent and the aircraft hit the ground very heavily and broke up. This accident was not the subject of an on-site investigation.