Is it too late to counter a readied spell that has been triggered since you cast the spell on your turn and "hold it" until it triggers?

— Tyler Ryan (@TySQL) August 4, 2017

Counterspell foils the casting of a spell, not the release of a spell that was cast previously using the Ready action. #DnD https://t.co/oHRArNszUN

— Jeremy Crawford (@JeremyECrawford) August 4, 2017

4 a slight delay, a wizard can b counterspell proof. Can a wizard make the trigger of her ready the end of her turn? Could be done each turn https://t.co/SiTsXP9Q5H

— World of Farland (@Farland_World) August 4, 2017

The trigger you choose for the Ready action must be a "perceivable circumstance" (PH, 193). A caster doesn't perceive turns ending. #DnD https://t.co/Yh1KHFFjXI

— Jeremy Crawford (@JeremyECrawford) August 4, 2017

If they’re looking for a slight delay after their turn, they can just set the trigger to “the moment someone acts after me”That works, but you act after the trigger, which might end your concentration on the spell.

— Jeremy Crawford (@JeremyECrawford) August 4, 2017

Got it. Then the first perceivable activity of the creature that goes immediately after the wizard? This ruling seems abusable. https://t.co/EsieO19XVV

— World of Farland (@Farland_World) August 4, 2017

A readied spell requires concentration & you release it after its trigger occurs. If you take any damage, your concentration might end. #DnD https://t.co/GBpbeb7N13

— Jeremy Crawford (@JeremyECrawford) August 4, 2017

Oh I see. So the wizard can be counterspelled at the time she takes the ready action.

— World of Farland (@Farland_World) August 4, 2017

When you use the Ready action to cast a spell, you cast the spell when you take that action and can be counterspelled then. #DnD https://t.co/hVnXGoqvTu

— Jeremy Crawford (@JeremyECrawford) August 4, 2017