August in Istanbul features warm afternoons and evenings but comfortable late nights and early mornings with mostly sunny skies.
Daytime high temperatures during August tend to average around 29 C (84-85 F) early in the month, cooling gradually to 27-28 C (81-83 F) near the end of the month.
A few of the warmer afternoons, especially early in the month, can reach up near 32 C (90 F). The record high temperature in Istanbul during August is 40.5 C (105 F).
Late night and early morning low temperatures tend to average around 20-22 C (70-72 F) early in the month, falling to 19-20 C (66-68 F) near the end of the month.
A few of the cooler mornings, especially late in the month, can dip down near 16C (61 F).
The record low temperature for Istanbul during August is 8 C (46 F).
How Much Sun and Rain
About 28-29 days this month will see sunny, or at least partly sunny skies with only 3-4 days recording any measurable rainfall.
The number of daylight hours will decrease this month from about 14.3 hours on the 1st to about 13.2 hours by the 31st.
Wind speeds during this month will be mostly gentle to moderate at 12-28 kph (8-18 mph) but can occasionally be fresh at 29-38 kph (19-24 mph).
The beaches near Istanbul lie mostly along the shores of the Sea of Marmara and along the Bosporus Strait.
The sea temperature is warm throughout the month, averaging between 23 C and 25 C (74-77F).
What to Wear in Istanbul in August?
During the summer it is best to wear light airy cotton clothing with a hat and sunblock since most days will be sunny.
A light sweater will come in handy for the cooler late evenings or early morning hours.
Sundresses and knee-length skirts/shorts and t-shirts and jeans are ok in Istanbul, however, when visiting a Mosque, women must cover their hair, upper arms, shoulders, and knees.
Things to Do in Istanbul in August
This month should have plenty of nice, sunny weather, so it's a good time to consider going on a pay-what-you-wish walking tour of Istanbul.
If you manage to visit on a particularly clear day, consider visiting Galata Tower to enjoy one of the best views of the city from above.
On especially hot days, you'll want to stay indoors as much as possible, which makes the cool and dark Istanbul Aquarium.
Here are a few other ideas:
Ocean Weather Services