I don't know. We need more information. Are they in an incubator or do you mean they are being laid when the temperature is 30F? Is it 30 in the nest or outside?
How long are they exposed to the lowest temperature?
Broody hens stop laying. It's how nature ensures that all the eggs hatch within a few days of each other. A broody hen will sit on the nest all day and all night, only getting up once or twice a day to eat, drink, and poo.
If she's still laying eggs, she isn't full on broody yet.