How can I make a "lean to" roof over my deck so rain doesn't blow in?

First thing you need to consider Janjan is if your deck is built solid enough to hold the weight of a roof. Most decks need extra support added if the original deck was never meant to support a roof. If you can add support posts for the roof on the outside of the deck and attach a lean to roof to your house it would be better. You will also need to check your local building codes.

https://www.decks.com/how-to/475/how-to-build-a-roof-over-a-deck

myoutdoorplans.com/shed/12x16-lean-to-shed-roof-plans

https://www.front-porch-ideas-and-more.com/building-a-porch-roof.html

You have a lean-to roof now?

If you don’t, you’re going to need a grander and probably a Building Permit.

Roof framing is a structural modification.

Roofing has to be rated for 85MPH winds on houses and when you get your Permits, you’ll find out how your city interprets accessory structures, like an enclosed deck.

Around here on the Oregon coast they use polycarbonate panels s lot for a roof that lets in some light and keeps the rain off.... https://www.google.com/search?q=pictures+of+polycarbonate+porch+roof&tbm=isch&source=univ&client=opera&sa=X&ved=2ahUKEwjNz6_ulaLkAhWDIDQIHW7dB14QsAR6BAgHEAE&biw=1473&bih=695 we regularly get winds of 60 mph

https://www.youtube.com/watch?v=nheUhggR0oM

A pergola with a roof is nice like this: https://www.pinterest.com/pin/788411478489186351/?lp=true

Hope this Helps! Jeremy - https://do-daddy.com

Hello Janjan, have you thought of a large hard top gazebo? You can add sides that keep the rain and bugs out, never worry about taking the "cover" off in the winter

https://www.walmart.ca/en/ip/sojag-pompano-wall-mounted-gazebo-10x10ft/6000199790041?cmpid=sem_google_en_pla_none_1342213373_56613074809_None&gclsrc=aw.ds&&gclid=CjwKCAjwnrjrBRAMEiwAXsCc45OatdYGipO7OUrz_rMYQ10gcP5PZrh7dme3D_Sc24WzIIzRTNqHhBoCjLkQAvD_BwE&gclsrc=aw.ds