Starting with the March Heatwave, this is something that I hold close to my heart and still think about regularly and frequently. This event sparked awe in me I've never felt before in any other weather event and was literally as much fun and engrossing as tracking a major hurricane threatening landmass. What really put this over the top was 1. It actually affected my backyard as much as everyone else unlike 90% of the extreme weather events I follow and 2. I wished this to happen and beforehand it was a wild dream. I tracked this start to finish and absorbed the maximum amount of information possible where I was literally spending everyday and all day following everything that was taking place. Its such a large event that I can only summarize it in a few short ways: It was the most extreme meteorological event in North American history (statistical and stated by one of the US's leading climatologists), it is estimated that such a heat wave with the kind of anomalies experienced only occurs once every 4000 or so years, countless number of records broken but I believe the number is around 7000 which doesn't include humidex or high lows which were even more impressive and numerous, Capped off the winter that wasn't, broke records often by more than 6ºC for numerous days in a row (in some cases over 15ºC), various times the record high was broken by the lowest temperature of the day, and set off ripple effects that were extraordinary across NA. What was the kick-off to the insanity was a severe thunderstorm line that roared through southern Ontario on March 15 that EC did not issue warnings for because they were caught off guard but this severe thunderstorm actually was the 2nd worst thunderstorm I experienced during the year!! It had lima-bean sized hail and knocked out the power very briefly...all this in mid-March!?! That has never happened and I couldn't believe it. Normally we're buried in 40 cm of snow and freezing still but got a storm that brought some of the largest hail I've seen since hail that size is uncommon in mid-western Ontario. By the way, that happened in the middle of the night without the daytime heating making it more absurd. After that it was so bizarre how the atmosphere "switched" to a summer mode where all the clouds had volume to them instead of the flat overcast nonsense we put up with for months. The heatwave easily crowned this as the "warmest Spring warm-spell" that occasionally happens like March 8, 2000 and early April 2010. All I can say is I couldn't have been happier.
Today a year ago was also the mini-tornado outbreak in Michigan where 3 tornadoes occurred...one being an EF3 that hit Dexter MI. It is very rare to have March tornadoes in Michigan and only a small handful have occurred. I had a feeling there would be tornado weather on March 15th in southern Ontario but the parameters lined up better in MI. Also in general, this March period helped set up the conditions of the huge drought of 2012. Back to the severe weather though, here is what I think was a Supercell over the cool Lake Huron waters of mid-March:

Link to March 2012 Records Thread: viewtopic.php?f=24&t=112540&start=0