The charts on this page show the probabilities of receiving a certain temperature on a certain day. Some examples that might help:
Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
---|---|---|---|---|---|---|---|---|---|
First 16° | Oct 18 | Oct 24 | Oct 28 | Oct 31 | Nov 3 | Nov 7 | Nov 10 | Nov 14 | Nov 20 |
First 20° | Oct 10 | Oct 15 | Oct 19 | Oct 22 | Oct 25 | Oct 28 | Nov 1 | Nov 4 | Nov 10 |
First 24° | Oct 1 | Oct 7 | Oct 11 | Oct 15 | Oct 18 | Oct 22 | Oct 25 | Oct 29 | Nov 4 |
First 28° | Sep 19 | Sep 24 | Sep 28 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 14 | Oct 19 |
First 32° | Sep 14 | Sep 17 | Sep 20 | Sep 23 | Sep 25 | Sep 27 | Sep 29 | Oct 2 | Oct 6 |
First 36° | Sep 8 | Sep 11 | Sep 14 | Sep 16 | Sep 18 | Sep 19 | Sep 22 | Sep 24 | Sep 27 |
What's a safe temperature for tender plants? When the nightly temperature falls, frost can form, even above 32°, because the air is colder high above the ground and the frost can form up there and then fall down onto your garden and do some damage, even if it's 36° on the ground. So many factors come into play, including wind, concrete, houses, trees and other structures, etc etc etc. Because of all this, you might want to consider 36° as "the danger zone".
In your average springtime, you have a 90% chance that there will be no 36° nights by June 10. In other words, you can pretty much count on being safe from frost by that day. But we want to get those tomatoes in the ground as soon as possible, right? We see that there's still an 80% chance of 36° on May 14, so we don't dare plant that early. We wait a few days and by May 25 we are at the 50/50 point. At this point, we are close and we can start watching the weather forecast. If the upcoming week's forecast doesn't show below 40°, then it's probably okay to risk planting out your plants. If conditions change and a surprise frost does threaten, there's always things you can do to protect plants from frost.
Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
---|---|---|---|---|---|---|---|---|---|
Last 16° | Apr 13 | Apr 8 | Apr 4 | Apr 1 | Mar 29 | Mar 26 | Mar 23 | Mar 19 | Mar 14 |
Last 20° | Apr 16 | Apr 12 | Apr 9 | Apr 7 | Apr 4 | Apr 2 | Mar 31 | Mar 28 | Mar 24 |
Last 24° | Apr 26 | Apr 21 | Apr 18 | Apr 15 | Apr 12 | Apr 10 | Apr 7 | Apr 4 | Mar 30 |
Last 28° | May 13 | May 8 | May 4 | May 1 | Apr 28 | Apr 25 | Apr 22 | Apr 18 | Apr 13 |
Last 32° | May 22 | May 17 | May 14 | May 11 | May 9 | May 6 | May 3 | Apr 30 | Apr 25 |
Last 36° | Jun 10 | Jun 4 | May 31 | May 28 | May 25 | May 21 | May 18 | May 14 | May 8 |
Now that you know your frost dates, use our Garden Planting Calendar for Cambridge, MN to know when to sow and transplant your various vegetable plants!
Data is provided by the NOAA National Centers for Environmental Information. Photography by Garden.org member TBGDN.