The silly season is the period lasting for a few months (starting in mid- to late summer) in the United States, the United Kingdom, Ireland, Canada, New Zealand and Australia typified by the emergence of frivolous news stories in the media. This term was known by the end of the 19th century and listed in the second edition of Brewer's Dictionary of Phrase and Fable and remains in use at the start of the 21st century. The fifteenth edition of Brewer's expands on the second, defining the silly season as "the part of the year when Parliament and the Law Courts are not sitting (about August and September)".
Typically, the latter half of the summer is slow in terms of newsworthy events. Newspapers as their primary means of income rely on advertisements, which rely on readers seeing them, but historically newspaper readership drops off during this time when in the U.K., Parliament takes its summer recess, so that parliamentary debates and Prime Minister's Questions, which generate much news footage, do not happen. To retain (and attract) subscribers, newspapers would print attention-grabbing headlines and articles to boost sales, often to do with minor moral panics or child abductions. Other countries have comparable periods, for example the "Sommerloch" (summer [news]hole) in Germany and the "Komkommertijd" ("cucumber time") in Dutch or "Agurktid" (also "cucumber time") in Norwegian and "עונת המלפפונים" (read: "Onat Ha'melafefonim" again meaning, "cucumber seazon") in Israel. French has the dull season la morte-saison, and Swedish has the news drought nyhetstorka.
The Dutch and Norwegian expression of "cucumber time" (which also exists in German as "Sauregurkenzeit") is actually derived from an old English expression from the 1700-hundreds which, while no longer used in Britain, is still used in Norway, the Netherlands, Poland (Sezon ogórkowy) and also in Hungary (Uborkaszezon). A silly season news item is called "Rötmånadshistoria" in Sweden and "Mätäkuun juttu" in Finland, both literally meaning "rotting-month story".
A side-effect of stirring up the public in this manner comes when an authentic story is dismissed as a prank, or when a superfluous story is taken as legitimate (cf: The Sun, The National Enquirer etc).
In Australia and New Zealand, the silly season has come to refer to the Christmas/New Year festive period, which are in the Southern Hemisphere summer. In Northern Australia, silly season refers specifically to the build up to the wet season, when the heat and the high humidity cause people to act a bit strangely, since rains haven't come. During this period, suicide rates are also marginally higher.
It also refers to off-seasons in sports, such as football, Formula One, NBA, or NFL - where due to lack of action on field/track, speculations are instead made on possible team changes and debuts of any star involved in the sport. However, it is used as a year-round phrase in NASCAR, as changes occur on a full-time basis and there is no so-called off-season.