When I was a kid, we'd cover our tomato plants with a metal gallon can with the bottom cut out and the top halfway cut out and bent upwards. The top opening would be facing east to get morning sun and shade in afternoon. These cans make very effective windbreaks and hold in a bit of warmth on cool nights. After a couple or three weeks, the plants would be hardened off and we'd remove the cans. I've been collecting cans so I can do that again. Nowadays we have floating row cover, so I think I could set them out even earlier knowing that it would be easy to cover them with the row cover on really chilly nights. It's hard to find those cans nowadays, but some schools and other cafeterias still get food in them. Maybe you can find some there? Or at your local recycling center?

Squash and melon transplants are both summer/warm season crops usually planted out after tomato plants go in. You can go early with them with some of the many season-extending tricks. Additional soil preps like warming with black plastic mulch down a couple of weeks before planting, low tunnels, cloches, row covers, WOWs, cold frames, etc. But without advance prep and extra protection you just get stunted unproductive plants, stressed, prone to disease. That is the primary reason why direct seeding them works best. They don't germinate until the soil temp is right and pop out of the ground already mostly adjusted to the climate. They may still need some extra protection if the weather changes a great deal but they tolerate it better. In short-season gardening areas learning all about the methods of season extending, both spring and fall, is your best friend. Improves your odds of success 100 fold. Dave Here is a link that might be useful: Season Extension Techniques

My car worked great as the transition from the house to the garden. Use plastic totes for easy unloading when you need to haul around people instead. Also keeps my car seats clean. I spread a towel or blanket just in case because on some days I was able to put the plants directly out on sheets of cardboard for some direct sun as I increased the amount of daylight. I try to give them 2 weeks at least to harden off, but I might be too cautious. I coddle the tomatoes & cucumbers a lot because we have a lot of cloudy 50 degree days yet in spring. It's tricky to have the starts ready, but not pot bound by the time the soil has warmed up enough.

I have found strawberries to be very hardy, and I live in Z5. I would suggest get them in the ground with some water. Water every other day for a week. Put something in front of them, and close, for a few days, like a board, to prevent sun burn. The sooner they can start getting acclimated, the better. Always an...Angel