The 34-year-old is set to feature in four matches for the Welsh county, which started with their fixture at Colwyn Bay against Lancashire on Sunday.
But he remains available for selection by the Outlaws in the Vitality Blast, and can be recalled by Nottinghamshire at any time.
“Knowing in advance that I’m set to miss out on selection for Scarborough has given Glamorgan time to come in for me on a loan deal. I’m gratefulto them for the opportunity,” said Patel.
“I’ll keep giving it everything for Notts in the Blast, so overall I’m looking forward to a positive end to the season across both formats.”
Patel’s time with Glamorgan is also set to include fixtures against Worcestershire, Durham, and Leicestershire, as the former England all-rounder looks to add to his career tally of 222 first-class appearances.
“There was absolutely no reason not to let him go out on loan and play some first-class cricket,” said Notts director of cricket Mick Newell.
“It’s a higher standard than the second team and we can recall him ahead of future matches should we decide we want to pick him.”