USDA Zones are based on minimum temperature likely to be experienced during the winter: https://www.usna.usda.gov/Hardzone/hzm-ne1.html
According to the above map and table, with the temperature at 24Ã‚ÂºF inside a double floating cover and a 4mil plastic covered area in my garage in which I have a fluorescent light on 24/7 and am trying to overwinter a couple of containers of Pineapple Sage and a Heliotrope, as well as a tiny Japanese Maple seedling, and a few other things, it is USDA Zone 9a -- same as Houston, Texas and St. Augustine, Florida. That should mean next winter, I should be able to overwinter a dormant fig tree there.....
OK, I just re-read your post and your question is about wind-chill temperature. Sometimes, my outdoor thermometer registers the wind-chill temperature that is being forecast/reported so....
In simple terms of considering whether a plant is hardy in my area or not, I always go with hardiness one zone colder than mine unless it's something I really really want and am willing to go extra length to protect it. Also, there are always micro-climate around your property, against the south side of the house wall, if you have masonry wall as opposed to aluminum or vinyl siding will make a difference too.
In addition, I try to purchase from nurseries that are same or one or two northern zones when cold hardiness is in question, and purchase from nurseries that are same or one or two southern zones when heat tolerance is in question.
-35Ã‚ÂºF huh? BRRR!!!!