Turkey in August

I was in Turkey (Istanbul) the last week of April and it was very crowded. The visitors for the 100th anniversary of the battle of Gallipoli (April 25) certainly added to the crowd, but I understand that Istanbul is very crowded from April onward, and added to the tourists arriving by plane there are several cruise ships docking almost daily.
I think that August may be worse since school is out then and people take family vacations.
The weather was very hot a fews days in April so I imagine that August would have all hot days.
Just be prepared for long lines to enter the major sites and a lot people hanging out at the park between the Blue Mosque and
the Hagia Sofia.
Still if August is the only month you can take vacation then I say go for it. Turkey/Istanbul is a beautiful experience.

What would be a good time? I am going with my cousin. Her daughter is a school counselor and she can only travel during school holidays.

Some parts of Turkey can be cooler, for instance along a more open coast. Cappadocia can get snow in spring, but you wouldn't expect it in summer. Various towns could also be less crowded, but I assume that you mostly will be visiting popular highlights, if you don't have a long trip.

If by school holidays, you mean Christmas and Easter holidays as well, then Easter.

Definitely Easter - and if it falls a little later in the year (did not check the dates for next year) then you may be in time for the tulip festival which means tulips everywhere in full bloom and especially in Gulhane Park, the area near the Topkapi Palace and the park between the Blue Mosque and Hagia Sofia. It was one of the perks where we were there.

Easter time in Istanbul is insanely busy,yes the city is so pretty with all the spring flowers but the crowds are crazy.August is hot but not unbearably so,maybe .c30-32oC.It is busy(when isn't Istanbul busy these days?) but not as much as one would imagine.At this time of year European visitors tend to take coastal holidays,some may hit Istanbul just for a day or two front or back of that but they aren't there for longer and Istanbullers themselves also head for the coasts too.

Thanks Sari.... I guess I thought that being a Muslim country, Easter would be quieter. It's hugely busy here because of the Christian sites. I guess a lot of Europeans flock to Turkey during the holidays to escape the crowds of tourists that come to their home cities :-)

Many Greeks visit Istanbul at Easter(ironically!)plus there is the city's own Christian community,plus....it is tulip time and that alone draws people from the whole world over.I went with friends one Sunday in April to see the tulips in Gülhane Park but we got to the gate and it was just a solid wall of human flesh.We couldn't even see the ground never mind a single tulip!,so we just turned around.Early the next morning it was almost empty so we could stroll at leisure but by 11.00 it was once again getting very full so again we scooted.
So for me Easter-time,although usually great weather wise,is a bit too full on for a pleasant visit.