Dark Sky used to have historical weather data for a specific address that one wanted. Is there a way to still access this?

That does not appear to be one of the Dark Sky features that has been incorporated into Weather. You can let Apple know it's something you'd like to see here:

Product Feedback - Apple

Alchemy4 wrote:

The historical weather is helpful to farmers. I can’t get my insurance claim without it!

As Dark Sky was merely an app that accessed other services' data, I'm sure there are other sources of historical weather data. As an example, a quick search turned up this:

https://www.wunderground.com/history

Is there a plan in apple weather for including the historical data that was available on Dark sky. It is missed

Questionsforconsideration wrote:

Is there a plan in apple weather for including the historical data that was available on Dark sky. It is missed

Only Apple would know that and they haven't said.