Summers are hot and the rest is cold. =)
Really from about June through August it is hot...always in the 90's or above. Its not as bad as it sounds though and most Boise folk still keep their normal routine. Fall is short and does give us some nice days, but by November it is cold and chilly. It stays that way until May. Then it begins heating up again. Everyone complains about the cold (or the hot), but we don't mind it much either because its nothing too extreme. That's the best thing about Boise weather...it can be "too hot" or "too cold" but we never see the crazy weather you hear about on the news in other parts of the country.
And of course getting outdoors is one of Boise's biggest traditions and there are chances for that all year round. :)