Milwaukee's May freeze history; gardening, planting season begins

A dreary end to April might have gotten you into a planting mood and eager to get your hands in the dirt, but are we in the clear for 2023? 

If you use native species, you might have started planting weeks ago – but European and Asian species more susceptible to cold air, and May can be very hit or miss for Milwaukee. But if you have the itch, there might be some good news for you. 

Common violet, already in full bloom in April, can handle late frosts and freezes just fine

Looking at historical data of Milwaukee freeze times, on average, our last freeze is April 24. The latest we've ever had a freeze on record is May 27, and the earliest we ever had our last freeze is March 29. Basically, we can vary in last freeze dates by almost two months. You have to love Wisconsin weather. 

But if you want to play the odds, in the last 30 years we've only had a last freeze in May five times – most recently in 2020 and 2004. Overall, there is only about a 1-in-6 chance that from here on we'll have another freeze historically. 

Milwaukee's area freeze statistics since 1871

To back that up, our temperature outlook heading into mid-May is looking warmer than average. Average highs during this time sit in the mid-to-upper 60s. Generally, lows sit in the mid to upper 40s. So completely based on this forecast, and based on historical events, it is unlikely we have another freeze moving forward. But we're never truly in the clear until June.

Local gardeners often use the rule of waiting until after Mother's Day to plant. 

Temperature outlook from May 10-16

40 or colder temperature statistics for Milwaukee

What about extra-tropical plants? Or setting out lawn furniture? The last 40-degree low or colder generally doesn't happen until May 20. It's happened as early as April 22 and as late as July 1, so once again we have a range of over two months with that one. 

Bottom line: Spring takes its sweet time to arrive quite frequently. Our second week of April was a cruel taste of warmer air, but it does look like better weather is coming no matter what!