The climate in Istanbul is temperate oceanic. The summers are hot and humid and the winters are cold and wet, with occasional snowfalls. There is a surprisingly high amount of rain in the city, more than that of London, Dublin, or Brussels. Rain is most common during the late fall and winter months. Spring and summer are the driest times of year, although there is no time that is considered a "dry" season. Summer months can be quite hot with average temperatures around 27 degrees during the day. Humidity makes it feel even hotter. Winter is cold and damp with temperatures reaching 7 degrees Celsius during the day.
SightsMany of Istanbul's historic sights are found in Sultanahmet. These include the Hagia Sophia, Topkapi Palace, the Blue Mosque, and Basilica Cistern. Outside of this neighborhood there is also the Church of St. Savior in Chora, the Galata Tower, and the Galata Whirling Dervish Hall.
NeighborhoodsSultanahmet is the Old City in Istanbul. This is where you will find most of the historic sights including the Blue Mosque and Hagia Sophia. The New City is the main business center and has a much more modern atmosphere. There are many shopping areas and popular districts such as Elmadag, Nisantasi and Etiler. The Bosphorus is lined with beautiful palaces, parks, and mansions. Along the Bosphorus there are popular areas such as Besiktas and Ortakoy. Other neighborhoods include the Golden Horn, where you'll find Eyup, and Princes' Islands, which offers a wonderful retreat from the hustle and bustle of the city.
ActivitiesHamams, or Turkish Baths, are great places to visit while you're in Istanbul. Most neighborhoods have at least one Hamam, but they each vary in cleanliness and quality, so ask around for a recommendation.
Another popular activity is smoking a hooka, or water pipe. There are a good number of places near the Grand Bazaar where you can smoke a hooka.
A Bosphorous Cruise is another great activity.The best option is to take the cruise offered by the state run company Sehir Hatlari. The cruise is 90 minutes each way or you can take a 2 hour non-stop cruise. During the peak season there are three daily departures, but it is still best to arrive early. You can buy tickets near the Eminonu terminal just east of the Galata Bridge.
Food and DiningAs you walk around Istanbul, restaurant employees will do their best to persuade you to come into their restaurant. This is particularly true in the touristy areas. They are generally friendly and welcoming, so a smile as you decline can go a long way. There are plenty of affordable restaurants and fast food options in Istanbul. Many of the restaurants in Sultanahmet are geared towards tourists. Taksim has some wonderful restaurants that are upscale in style but still reasonably price. Affordable food options include doner, hamsi and kumpir. Pastry shops are spread throughout the city and have some very delicious desserts that are reasonably priced. Look for one with a rooftop patio so you can enjoy a view of the city at night.
TransportationAlthough the public transportation system can seem chaotic, it is the best way to travel around the city, particularly when you're on a tight budget. The light rail system has four underground metro lines, four Tramvays, which are aboveground, two Funikulers, two mini-lines, and the Marmaray, or underwater lines. There are also ferries that travel the Bosphorus frequently. The above ground trams must deal with traffic, so they can be frustratingly slow, particularly during rush hour. If you're hoping to explore the Bosphorus, just hop on one of the ferries. These are cheap and efficient, and far more affordable than any private tour that is available.
Private dolmus minivans also follow set routes and offer a good option late at night. They are not on a set schedule but instead wait to fill up before departing. They do run through the night, unlike the public transportation system.