I know that things vary every year, but when is the peak fall color normally in Kiev? Late September? October? I have 2 weeks there where I will be volunteering, and since I enjoy photography, I was hoping to photograph the fall colors in my free time.
In the warmer years its early to mid-November. In colder years its mid to late October. You will get most vivid colors in the West of the country, in the Carpathian Mountains. Mid to Late October is best there.
Ukraine in general, and Kiev in particular, has a lot of foliage and parks. Spectacular shots are from right bank over the Dnipropetrovsk (river). Botanical gardens and St. Volodimir park (from St. Michael's monastery, down and through the St. Volodimir statue) are spectacular. Full range of lenses can be used, but medium to wide-angle will be most useful. Open air architectural museum of Pirogovo RC Pilots (on the outskirts of the city) provides great photo ops in any season. Enjoy!
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I would opt for mid of October. Last year it was November due to unusually warm autumn.