Heavy rain hit the Losail circuit overnight, with more falling throughout the day, while storms are forecast for Saturday evening.

Riders are not convinced running under lights in the wet will be safe, despite a trial by officials conducted earlier this year.

That has raised the possibility the 2017 season opener could be rescheduled, to either earlier on Sunday during the day, or even to Monday night, as was the case in 2009, if the conditions are not suitable for racing.

The three practice sessions completed so far have been in the dry, but organisers have scheduled an additional 20-minute session for 6pm local time on Saturday, for MotoGP competitors to assess the track.

Some riders have also expressed concerns that the wet circuit would lack grip, and that evaluation session will be followed by a Safety Commission meeting at 6:30pm, where the balance of the schedule will be discussed.

The times for fourth practice, from 7:55pm local time, and qualifying, 8:35pm, are currently unchanged.

UPDATE: The extra session scheduled for 6pm has been "delayed until further notice" due to track conditions.

UPDATE 2: At 6.06pm local time, the planned extra session was cancelled, as certain parts of the track were too wet while others had nearly dried out completely.

It remains unclear how this will affect the schedule moving forward.

UPDATE 3: Following a lengthy track inspection, it was announced at 7:40pm local time that FP4 will take place at 20:30pm - 35 minutes behind the original schedule - subject to conditions.