Based on my prior knowledge, the relationship between the season feature and the grain yield of soybean cultivar can be analyzed as follows:

- Low grain yield: The soybean cultivar may have a low grain yield if it is grown in a season that is not suitable for its growth. For example, if the cultivar requires specific temperature or photoperiod conditions that are not met in a particular season, the grain yield may be low.

- High grain yield: The soybean cultivar is more likely to have a high grain yield if it is grown in a season that provides optimal conditions for its growth. This could include seasons with the appropriate temperature, photoperiod, and precipitation levels.

Based on this analysis, here is the dictionary with typical season values for each target class:

```json
{
	"low": [1.0, 1.5, 2.0, 2.5, 3.0],
	"high": [3.5, 4.0, 4.5, 5.0, 5.5]
}
```

Please note that the specific values mentioned in the dictionary are arbitrary and can vary depending on the actual data and prior knowledge.