It would depend on the seedlings you are growing. Cabbages can go out in cooler temps than tomatoes and so on. What have you got?

Hi Flora_uk, thanks for your reply. Sorry I haven't been checking because the temperature have been cold anyway....

I have some marigolds, celosia, and salvia. According to the seed packet, I can start them outside now (since we have past our last frost date). Does that mean I can harden my seedlings off now? Or could it mean that I don't have to worry about hardening off and can move them outside directly since there won't be any frost anymore?

The weather forecast says for the next 10 days, the minimum is 41.

For my maters, if nights get below 55 or it's going to storm, it will be too much for them & I bring them in. For the peppers, nights below 60-65 are when I bring them in. My first set of mater & pepper plants have now been outside for 3 days & are doing great! Gotta bring them in today though. We're getting that storm front that hit the midwest with all the tornadoes & such today through tomorrow night, so temps are supposed to drop to the high 40's.