blackthorn winter

Etymology
So-called because it (typically) falls when blackthorn is flowering.

Noun

 * 1)  A period of cold weather in spring or early summer (March, April or May).
 * 2) * 1888 May 19, The Saturday Review of Politics, Literature, Science and Art, section Blackthorn Winter, page 590:
 * An inveterate custom of English conversation, combined with the engaging versatility of the English climate, from which the custom derives both its origin and its vigour, must be our excuse for devoting some specific attention to this branch of the English weather. [...] In similar fashion we made observe, mutatis mutandis, of the blackthorn winter that, though small, it is peculiarly bitter. [...] Providence does not invariably temper the wind of the blackthorn winter for him. On the contrary, he too often finds that a balmy north-easter will effectually temper the rise of the May-fly, [...]
 * 1) * 1888 May 19, The Saturday Review of Politics, Literature, Science and Art, section Blackthorn Winter, page 590:
 * An inveterate custom of English conversation, combined with the engaging versatility of the English climate, from which the custom derives both its origin and its vigour, must be our excuse for devoting some specific attention to this branch of the English weather. [...] In similar fashion we made observe, mutatis mutandis, of the blackthorn winter that, though small, it is peculiarly bitter. [...] Providence does not invariably temper the wind of the blackthorn winter for him. On the contrary, he too often finds that a balmy north-easter will effectually temper the rise of the May-fly, [...]

Coordinate terms

 * see