Not sure when you can start planting outdoors? Well How do gardener has a really cool chart on frost and freeze dates. Using the chart you can look up your own frost and freeze dates by city and state. If you exact city isn’t on the chart you can just look up a city that is in your area to get the dates.
There is also one for Canada, SEE THE SECOND LINK BELOW.
Freeze and Frost Dates in the US
Canada First and Last Frost Dates