When to Plant tomatoes?
The below graph shows the average daily temp since October 1 against some average minimums I have found as the preference minimum for tomatoes.
Note this is weather from my house. Tomato varieties are not all the same. There are some more cooler tolerant varieties that can set fruit when the weather is cool, and there are some heat loving varieties. The lower target of 11 is the bare minimum for some cooler tolerant varieties. 13 C is the general average however note if you buy heat lovers raised in controlled greenhouses that are not hardened off (look for purple stem) then 13 won’t cut the mustard when planted out. Set backs from cold weather will delay your harvests.
My advice when planting in Tasmania late October through to November, protect them on the cold nights (5 C or less), cold overcast days and from strong winds. You can see where the protection was needed by the dips in the graph below.