Can you successfully use Speed Dip in 30° temperature?

The majority of people have trouble with it at any temperature.

Seriously though, It's not going to freeze so I see no difference if its 30° or 90°.

I had bad results with the stuff. I went back to using Rickard logwood concentrate in a 5 gal pail. Melt a couple blocks of wax on top and you are good to go. Let the traps simmer awhile and when you pull them out they are waxed ready to go. I followed the directions to the letter with the speed dip and some were good but a lot were bad. Sometimes the old school is the best.

I dipped my traps in gasoline. Once.. & only once

I fully agree, temperatures shouldn't matter, that said I would rather have or buy slightly rusted traps than speed dipped traps, at this time of year run them as is and at end of season or beginning of warm weather clean the traps and do whatever prep they need for next season or for long term storage, For me, long term storage would mean tannin boil to convert rust and hot waxing to keep the air away from the steel thus preventing new rust. At seasons end I always figure that if I put the traps up like they won't be used again for years that they will always be ready for use at a moments notice or they can stay in the barrel for decades like some I haven't used since 1990 that are still trap line ready.
If you want to try Speed Dip or any other dip, starting in May gives you several weeks in which to try do overs and the gas will evaporate a bit better in warm weather.

I’m not a fan of speed dip myself... however, I’ve been told multiple times temperature makes a difference. It was explained to me that in order for the gas to evaporate, the temperatures need to be warmer, and dipping traps in cold weather would take them forever to dry. Personally, I’ve never got it to dry right no matter what I did though.

Degrease traps then dip in speed dip mixed with white gas / coleman fuel. If the traps are not degreased, they never dry. That's been my experience.