The planned half-hour Sunday morning warm-up session on the 2.258-mile, 13-turn permanent road circuit at Mid-Ohio Sports Car Course ahead of this afternoon's Honda Indy 200 was been delayed by almost two hours after heavy rain swept into the area just before the planned 8am start time.

Within minutes the circuit was awash with water and gravel traps started to resemble paddling pools. But the main reason for the session being able to proceed was to do with the medical helicopter which was unable to take off in the conditions with lightning in the area and even reports of tornados in the vicinity.

Teams and drivers had been relying on using the warm-up time to get the track into a race-ready condition, after Saturday afternoon's American Le Mans Series support race laid down huge amounts of the 'wrong kind of rubber.' Overnight heavy rain added to the uncertain nature of the track facing the drivers for Sunday's IZOD IndyCar Series race.

Worryingly, forecasts suggest that the atrocious conditions could last for several hours. While the most violent of the storms were set to pass through relatively quickly, new alerts were being issued for high winds, hail and localised flooding.

With the weather conditions still so uncertain, IndyCar was initially unable to say how they would be proceeding or what the stand-by contingency plans for the day might be, leaving teams and drivers in limbo every bit as much as the fans, many of who had camped overnight at the increasingly wet track in readiness for the race.

Conditions finally abated to allow a 20 minute warm-up from 9.45am local time during a lull in the worst of the conditions. However, there is still a chance that the start of the race itself could still be affected by the weather, although hopefully not to the extent of being unable to run at all on Sunday.

Full Sunday warm-up practice 3 times available.

While the IndyCar series does compete in the wet and has Firestone rain tyres available, extreme conditions can force an indefinite red flag just as happens in F1. In 2011, the Sao Paulo round of the season ended up being pushed over to Monday morning instead of the scheduled Sunday start time, but series officials will want to avoid that happening this weekend because of TV schedules crowded with Olympics coverage.

The uncertain situation means that IndyCar has not yet released an official starting grid for the race. As well as Alex Tagliani, it's now been confirmed that Helio Castroneves will also receive a ten-place penalty for an early engine change, after the Penske team decided to take the hit in order to ensure Castroneves had one of the latest-specification Chevrolet engines available to him for the race.

Although that will see him start from 23rd position on the grid, Castroneves is still expected to take part in the race despite injuring his hand in a coming-together with Mike Conway in the Saturday morning practice session.

Tony Kanaan is also unwell this weekend, having lost a substantial amount of weight during the week and being forced to skip the drivers' signing session on Friday due to illness. He's been visiting the in-field medical centre over the weekend for treatment.

Unofficial starting grid

1. #12 Will Power (C) Team Penske
2. #10 Dario Franchitti (H) Ganassi
3. #77 Simon Pagenaud (H) Schmidt-Hamilton Motorsport
4. #9 Scott Dixon (H) Ganassi
5. #2 Ryan Briscoe (C) Team Penske
6. #7 Sebastien Bourdais (C) Dragon Racing
7. #28 Ryan Hunter-Reay (C) Andretti Autosport
8. #26 Marco Andretti (C) Andretti Autosport
9. #67 Josef Newgarden (H) Sarah Fisher Hartman Racing
10. #22 Oriol Servia (C) Dreyer & Reinbold
11. #18 Justin Wilson (H) Dale Coyne Racing
12. #4 JR Hildebrand (C) Panther
13. #8 Rubens Barrichello (C) KV Racing Technology
14. #98 Alex Tagliani (H) Bryan Herta Autosport *
15. #27 James Hinchcliffe (C) Andretti Autosport
16. #14 Mike Conway (H) AJ Foyt Racing
17. #15 Takuma Sato (H) Rahal Letterman Lanigan
18. #11 Tony Kanaan (C) KV Racing Technology
19. #5 EJ Viso (C) KV Racing Technology
20. #19 James Jakes (H) Dale Coyne Racing
21. #38 Graham Rahal (H) Ganassi
22. #78 Simona de Silvestro (L) HVM Racing
23. #3 Helio Castroneves (C) Team Penske *
24. #83 Giorgio Pantano (H) Ganassi
25. #20 Ed Carpenter (C) Ed Carpenter Racing

* denotes ten place grid penalty for unscheduled engine changes All times and provisional starting grid are unofficial