Lightning strikes in the area surrounding Iowa Speedway forced the cancellation of Friday's opening IndyCar practice session on the 7/8th mile oval.
The session ran under green conditions for just a few minutes before the first spots of rain forced the series to throw a caution.
Increasing electrical activity resulted in red, and then chequered, flags being shown a short time later.
The morning outing was originally scheduled to the only practice session before qualifying, however AUTOSPORT understands that IndyCar is looking at options to tweak the day's schedule to allow the teams additional time to prepare for the first short-oval race of the season.
At the time the session was stopped James Hinchcliffe was fastest with a best lap of 17.5249s at 183.647mph.
The only incident of note involved the Canadian's Andretti Autosport team-mate Ryan Hunter-Reay, whose car shed a rear wing endplate shortly after taking to the track for the first time.
Pos Driver Team/Engine Speed Time Gap 1. James Hinchcliffe Andretti/Honda 183.647mph 17.5249s 2. Tony Kanaan Ganassi/Chevy 183.562mph 17.5330s +0.0081s 3. Carlos Munoz Andretti/Honda 183.105mph 17.5768s +0.0519s 4. Charlie Kimball Ganassi/Chevy 182.536mph 17.6316s +0.1067s 5. Marco Andretti Andretti/Honda 182.255mph 17.6588s +0.1339s 6. Ryan Briscoe Ganassi/Chevy 182.049mph 17.6788s +0.1539s 7. Will Power Penske/Chevy 182.035mph 17.6801s +0.1552s 8. Juan Pablo Montoya Penske/Chevy 181.975mph 17.6859s +0.1610s 9. Scott Dixon Ganassi/Chevy 181.945mph 17.6889s +0.1640s 10. Ryan Hunter-Reay Andretti/Honda 181.903mph 17.6929s +0.1680s 11. Josef Newgarden Fisher/Honda 181.257mph 17.7560s +0.2311s 12. Simon Pagenaud Schmidt/Honda 180.245mph 17.8557s +0.3308s 13. Graham Rahal Rahal/Honda 180.154mph 17.8647s +0.3398s 14. Mikhail Aleshin Schmidt/Honda 180.117mph 17.8684s +0.3435s 15. Justin Wilson Coyne/Honda 179.964mph 17.8836s +0.3587s 16. Ed Carpenter Carpenter/Chevy 179.766mph 17.9033s +0.3784s 17. Helio Castroneves Penske/Chevy 179.722mph 17.9077s +0.3828s 18. Sebastien Bourdais KV/Chevy 179.508mph 17.9290s +0.4041s 19. Takuma Sato Foyt/Honda 179.333mph 17.9465s +0.4216s 20. Carlos Huertas Coyne/Honda 177.745mph 18.1068s +0.5819s 21. Sebastian Saavedra KV/Chevy 177.219mph 18.1606s +0.6357s 22. Jack Hawksworth Herta/Honda 173.298mph 18.5715s +1.0466s