Anyone living in Winnipeg should know better.
Never, EVER start your yardwork before the Victoria Day long weekend. God knows, I never start mine until June.
If you're one of my foreign (ie non-Winnipeg) readers, I'll explain it thus:
IT STILL SNOWS IN MAY IN WINNIPEG!!!
Just yesterday, on my street alone, I saw a number of people with their lawn sprinklers going full-bore, or power raking their lawns, planting or tending their gardens, etc. In fact, one of my neighbours was planting seeds and transplanting some bulbs into his garden when I got home from my rounds. I asked him if that was a wise thing, given our weather. He laughed and said "It's the beginning of May! Tomorrow's supposed to hit 19°C, so I have nothing to worry about". This from a guy who's lived in Winnipeg for most of his 65 years...
Well, my good friend, I'd say you DID have something to worry about, judging by how quickly you were in your garden this morning ;)
Meteorology isn't an exact science. Things can change at a moment's notice. Common sense should dictate (and historical Winnipeg weather should attest to) that.