Une giboulée is a sudden, brief, hard, and often chilly shower of rain or even sleet. Normally, in the north of France, people talk about les giboulées de mars — March showers — not the April showers we know in the United States.
Right now, our weather here in Saint-Aignan is weird and we are having giboulées du mois d'août. That's "(month of) August showers" — we had three or four yesterday in Saint-Aignan, not counting the one we got at midnight between Sunday and Monday, and another one late Monday night. Both the nighttime showers were hard enough to wake me up. The rain was splatting so loudly against the roof and the skylight windows that I couldn't ignore it. It didn't last long, though.
Do you know how to pronounce the name of the month of August in French? The word is août. Traditionally the word is pronounced the same as the French words ou (or) and où (where), which are all more or less the vowel [oo] of "hoot" or "boot" — it's a rounder sound in French, not so drawn out as the English, but it is approximately [oo] — one vowel, no consonants.
The accent on the U has no real bearing on the pronunciation, by the way. Often, the presence of the circumflex accent (^) on French vowels indicates that an old S has been dropped from the word. In English, where we have retained a lot of French words with their ancient spelling, the S is still there. Août in English is August. Bête is beast. Côte is coast. Pâte is paste. And so on.
But back to août. Often, you'll hear people say the word août pronounced as [oot]. Maybe that's because [oo], combined with the words for "the month of," becomes le mois d'août — [luh mwah DOO]. And that's exactly the same pronunciation as for le mois doux, which would mean the "mild" or "soft" or "sweet" month. It's kind of confusing. The pronunciation with the T, [oot], is less ambiguous.
The dictionary says the preferred pronunciation is [oo], but adds that more and more « couramment » — "in everyday language" — you hear people say [oot]. That's what I hear a lot. And sometimes, you'll hear people pronounce août as two syllables — the [ah] of English "father" plus the [oo] or [oot]. That pronunciation seems to be dying out. According to many, [oo] and [ah-oo] are starting to sound old-fashioned.
Août is the only one of the names of the months in French that has all this pronunciation stuff going on with it. Janvier, février, mars, avril, mai, juin, juillet, septembre, octobre, novembre, and décembre all have just one pronunciation each, with no exceptions or variants.