If you plan to tackle the towering mountain of Mount Kilimanjaro then you'll undoubtedly be spending a few nights in the small city of Moshi. There are some great opportunities to visit safari destinations as well, including more obscure options which most people don't see.
Moshi's proximity to nature and wildlife is extremely beneficial when planning an adventure to Tanzania. You may take part in the Serengeti (which is still a ways away) or you may show more interest in the closer Lake Manyara or Tarangire National Parks; additionally Mkomazi National Park is nearby and under-visited, so you'll feel you have the place to yourself!
Mount Kilimanjaro is the largest mountain on the continent, just begging to be climbed by ambitious hikers. If you plan to be among such travelers you'll want to plan some R&R before and after the trek and Moshi is your best option for doing so.
You're only a few miles from Kenya when in Moshi, so consider crossing the border to check another country off of your list. While there you can visit Tsavo National Park which isi the same ecosystem as Mkomazi; similar to how the Maasai Mara and Serengeti are really one in the same, if not for political borders.
Winter in Moshi is June - October which coincides with the dry season. Temperatures actually don't change much from season to season thanks to its proximity to the equator.
Summertime is considered to be October - March and while that's considered rainy season, the heavy rains run from March - May.
