Having had 3 diabetic pregnancies, I found that I was more likely to have sudden "bad" hypos than when not pregnant. I ended up doing blood tests at 2 hourly intervals during the night when they where most likely to occur (had to set my alarm clock) which was tedious but effective. I suspect that at this moment, the twice daily hypos are caused by your insulin doses being slightly higher than required, This could is be caused by the heat or something else.
Doctors seem to think that our bodies behave like obedient robots but they are not even if the human whose body it is is being "good". Your insulin doses are going to increase as pregnancy continues and you can only continue to do lots of blood tests and seek advice re changing your insulin dose. If you had had diabetes for a longer length of time you would be able to adjust the insulin doses confidently yourself. If you need to change your doses, contact your department that day for advice, do not be fobbed until the next appointment.
Remember most nurses and doctors probably know less than you regarding diabetes, unless they have specialised, Diabetes consultants can forget that you are a pregnant mum having a baby... rather that an interesting set of symptoms... if you have choice of diabetes nurses/doctors you have the right to specify who you want to see. I had to do this during my last pregnancy as the male consultant thought he was GOD so I opted for the lady consultant who was more empathic.
Good luck - it will all be worth it when you finally have your baby (and escape home from hospital to enjoy him/her)