If you'll type 'hardening off' in the search you'll find many discussions about all the details. In fact there is a long one running over on the Growing Tomatoes forum right now.

I would question why you are planting all those different things at the same time since you have a mix of spring and summer crops in your list that are usually planted at different times.

I'd also suggest a bit of difference in your hardening process - no reason why you can't do several brief periods within the first day rather than 24 hours down time in between. Put them out sheltered for an hour and if doing ok then leave them out. They only need to come back inside if they show damage from not being sheltered enough or if there is a drastic change in weather/temps.

Dave

I put my plants out in a plastic tub this year.

Works great, no tipping and protects from wind, but still enough for hardening. I left them out all day from day 1 without issues (it was a warm and overcast day), but they need gradual sun exposure. Plants thay havent been outside will start to burn in just a couple hours or less of direct sun.

They are outside now and are doing ok, highs sometimes barely reqching 60. The tomatoes and eggplants are growing. They come inside when temps drop below 50, which is most nights. It has become a cool May, I am going to have to plant them in less than ideal conditions. But I warmed the soil and will provide agribon. With lows of 40 forecast I will try to hold out another week.

I haven't grown arugula, but I believe that is a cool weather crop.

Your over thinking it. I've never lost a strong plant from not hardening off, even when a frost hit and most articles on this topic take things too excessively.

As long as there's not a strong wind or cold night you can harden them off indefinitely without bringing inside. If strong wind, place in less windy spot. If cold night bring inside. If temp not below 5C/41F can leave outside without covering or bringing it in. In addition, they sell mini domes that you can leave on during windy days and or cold nights.

Saturday's calling for "High 52F. Winds E at 15 to 25 mph. Rainfall near a half an inch. Locally heavier rainfall possible." I pretty much always get higher winds than forecasted. E.g., this is my weather station's wind report for May:

I stretched a tarp over a section of ramp leading to a deck, so that the tarp covers the top and about 2/3 or so of the sides. Any reason I shouldn't keep the plants under there on Saturday?

I don't see a problem with it. If they look like they are getting stressed bring them inside. Tomatoes should not have any problems. I have had heat off in my greenhouse since the end of April. This week I planted out 30 tomatoes. No problems with any of them (in NJ about same weather as you). Your eggplants may be more sensitive. Mine in the greenhouse have slowed growth considerably with the cold nights but are not as stressed as my peppers. Are your cucumbers and cantaloupe seedlings?