No idea how big your plants are but I would suggest covering them tonight and maybe each night for a while yet. Tomato plants don't do well even in the low 40's overnight.
I started two dozen plants in January one year and had them four feet tall and put them outside the end of May. These plants were healthy and strong and I plasticed them at night for the first week or so but then we got a bit warmer and I figured I should be good, they were dead within just a couple weeks of overnight lows in the low to mid 40's and possibly some lows in the mid to upper thirties.
If you don't have good plastic available, you can do individual plants with garbage bags if need be. Place some stakes taller than the plants around the plants and just slip the bag down over at night and hope for the best. My issue here is that we still have lows in the low 40's even in the middle of August, as yet I have never managed to get a single tomato plant to survive outside for a season yet in 10 years of trying. I have lost at least 325 tomato plants in my attempts, anywhere from new sprouts sprouted outside in June to the four foot tall plants started in January in the house to everything in between. We can get a day time high in mid August of 80 to 90 F and then be a low 40F that night. By the end of August we are generally cooling off again and most years we have to start building fires again about the third week of August. My situation is clearly more extreme than yours so you will certainly have better luck than I, but from my
experience you want to keep them above the 40's at night and in the 30's should really be avoided if at all possible.
I have a lot of experience at what temps kill tomato plants... lol... I have trouble keeping them going in my house at times when we are gone for too long, as I cannot
feed the fire and the household temps can drop into the 40's or even into the 30's on extreme occasions.
Good luck I hope your plants make it, losing my tomato plants is very frustrating for me...