It will be far less than the temp rise of a trace, because a trace assumes lateral heat flow only. The spokes are heatsinked by the pin and pours.
You can calculate it yourself! The resistance of copper is known, the dimensions are known, the current flow is known, and the thermal conductivity is known. You can make the assumption that current and heat flows are uniform (lengthwise) within the spoke, which won't be a bad guess.
Small spokes are fine at 10A, that's nothing special. I'd worry about direct connect at around, hrm, 60A let's say? (Scaling the spokes along the way, e.g. say, 10x10 mil x 4 spokes for 70 mil o.d. pads under 5A, 10x15 to 10x20 for 70-120 mil pads 5-15A, etc. A 60A pad is going to be pretty big, like 250 mils or more o.d., so will have quite a lot of copper coming off of it. Though I don't like to use direct connections up there, anyway;
terminals are better.)
Tim