Temperature specificiations on MOSFET Safe Operating Area
These are transient response curves. A single pulse of the power and duration in the table will cause the junction temperature to momentarily rise 150 - 25 = 125 deg C. If your starting temperature is higher, the allowed power is proportional. "Single" in this context means that enough time must pass before the next pulse to allow the junction to cool back to ambient, probably several minutes.

For steady state thermal calculations, it is usually easier to use the thermal resistance values.