Very hard to say without seeing the email in question, but yes, in general such emails are very regularly scams.
Does it say why it's going to be deleted?
Does it ask you to click on a link or call a phone number?
Usually unless you failed to pay for the storage, if you are subscribed to paid storage, Apple does not threaten any type of deletion in iCloud. If there was an issue paying for storage, Apple would usually just say your data may be deleted, but doesn't usually threaten to delete the entire account.
If nothing else, check your iCloud account on your iPhone and by logging in to https://icloud.com, if there is an issue, it will show up there as a notification.
Otherwise, yes consider it a scam.
click here ➜ Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support