How long ago did you eat/inject? There may be some of your last meal bolus working. Any fat in your meal slows the rate carbs are absorbed. You're still on fixed rates for meals, and in the honeymoon phase, where your own pancreas gives you insulin unexpectedly. The heat causes some of us to experience lower blood sugar than normal, but some people need more insulin when it's hot.
It's not an exact science and those of us with decades of living with diabetes sometimes have to take extra carbs or extra insulin. I'm afraid it's part of having type 1 diabetes.