Seedlings

I sowed seeds about a month ago. I kept in light airy room till seedlings came through but for the past 2 weeks I have had all the seed trays on my garden table Day and night. I covered in clear plastic to start with but now I don’t bother. They all seem ok and with this lovely weather 65oc in day and 45 at night I thought they would be ok. Am I doing long term damage or will they be ok if I continue leaving them out at night. I’m in Northwood Middlesex… if it was to start to rain heavy I would cover or if temp was to drop lower at night I would also cover x