What would be the DC to navigate through a heavy storm at sea?

I am working on Seafaring Navigation DC checks. I have found the following DCs based on the Wilderness Navigation table on page 112 of the DMG and the following quote on page 117:

As long as a ship is within sight of land, there is no chance of the vessel becoming lost.

but what I’m not sure about is what to do if they are in the middle of a heavy storm.

Terrain DC
Within Sight of Land Assured (0)
Open Sea (Clear Skies, No Land) Easy (10)
Open Sea (Overcast, No Land Moderate (15)

Page 118 of the DMG says:

If weather conditions indicate both a strong wind and heavy rain, they combine to create a storm with high waves. A crew caught in a storm loses sight of all landmarks (unless there’s a lighthouse or other bright feature), and ability checks made to navigate during the storm have disadvantage.

Should I just apply the Open Sea (Overcast, No Land) DC, or should it have it’s own DC 20 while the storm is ongoing, to avoid becoming lost at sea?