Memorial Day is known as the unofficial start to summer. However, here in the Upper Midwest, its also known as a holiday that can serve up any kind of weather. In just the past few years, the metro has seen a wide variety of temperatures and weather for this last Monday in May. Below is a graph of the past 8 Memorial Day Mondays here in the Twin Cities showing high temperatures varying over thirty degrees.
If we take a look at the modern day records, since 1970 for this sample, you can see just how extreme the temperatures can be on Memorial Day. Also, it appears that at least half of the time, some rain will fall on your BBQ.