Swords - Spring
Wands - Summer
Cups - Autumn
Pentacles - Winter
This is the most typical. Here's why--as Strega and others note, this follows the Wiccan alter (or circle) allignment: Atheme (knife/sword) to the East/Spring, Wand to the South/Summer, Cup to the west/Autumn and Pentacle to the North/Winter.
If you want a seasonal rational..well, it works really well if you're in a Mediteranian type of climate--In such a climate, you get windy springtimes, sometimes starting as early as Feb. Days are crisp, harsh and cutting, the wind blows firecely at night rustling the plam fronds--meanwhile, new plants and leaves cut they way up out of the earth. As Spring is the end of the school year, its a time for tests and studying, reading, writing. Also math for tax time.
Wands are pretty self-explanitory--hot, active, passionate. In that kind of climate, summer is hot and dry--and very active. Time for camping and traveling. Late nights around a bon fire.
Cups--Autumn means rain. If it's gonna rain, it'll rain then. So you stay indoors and get cozy. Time to share a bottle of wine or have a family gathering. Also, a psychic time--Halloween (or Samhain) when the spirit world comes near.
Pentacles--Winter is the Earth at rest--like pentacles, patient, solid. A time to stay indoors and be domestic, get some work done, inventory.
Mind you, this is just my rational. In the end, you decide which suit speaks to you of which season. If winter is cutting and windy and you figure it for swords, make it swords.