The Collaborative International Dictionary of English v.0.48:

Canicular \Ca*nic"u*lar\, a. [L. canicularis; cf. F.
   caniculaire.]
   Pertaining to, or measured, by the rising of the Dog Star.
   [1913 Webster]

   Canicular days, the dog days, See Dog days.

   Canicular year, the Egyptian year, computed from one
      heliacal rising of the Dog Star to another.
      [1913 Webster]

WordNet (r) 3.0 (2006):

canicular
    adj 1: of or relating to the dog days of summer; "the canicular
           heat of the Deep South"
    2: relating to or especially immediately preceding or following
       the heliacal rising of Canicula (the Dog Star); "canicular
       days"

Moby Thesaurus II by Grady Ward, 1.0:

63 Moby Thesaurus words for "canicular":
   aestival, arctic, ardent, autumn, autumnal, baking, blistering,
   boiling, boreal, broiling, brumal, burning, burning hot, ebullient,
   equinoctial, feverish, flushed, grilling, heated, hibernal, hiemal,
   hot, hot as fire, hot as hell, like a furnace, like an oven,
   midsummer, midwinter, out of season, overheated, overwarm,
   parching, piping hot, red-hot, roasting, scalding, scorching,
   searing, seasonal, seething, simmering, sizzling hot, smoking hot,
   solstitial, spring, springlike, sudorific, summer, summerlike,
   summerly, summery, sweating, sweaty, sweltering, sweltry, toasting,
   torrid, vernal, white-hot, winter, winterlike, wintery, wintry