I live near St.Louis and my gas was double what the previous 2 months were, but then again there was a 16^ average temp difference too. Going by previous months with that average temp (32), it is within those months usage. I have an Excel SS that dates back to 9/10 with average temps and usage stats.
If the previous months readings were wrong, the actual reading just got caught up. Once I had 3 months of estimated readings and when they did an actual I got hit. Since then I've gone to budget billing.