Use 'be no joke' to emphasize the difficulty or demanding nature of a situation or task.

Intensity Highlight

It's mostly used in conversational settings; not suitable for very formal writing.

Colloquial Use

Expresses frustration or respect regarding the challenge faced.

It stresses that something should be taken seriously and not underestimated.

Used to recognize and affirm something as factual or significant.

Emphasizes that something is not being exaggerated or overstated.