What happens if a utility transformer exceeds its ratings temporarily?

[Birken Vogt]

There is a 10 kw feeding my current house with 200 amp service. Where I grew up, there was a 10 kw from the 1940s, feeding 3 houses.

 

[Dsg319]

Will there be any noticeable voltage drop during the transformer being temporary overloaded?

I would think not but what do you say?