In thepast few years, yes. We've had warm winters in the past where it hasnt gotten above 20 degree's (F). In the summer it was 100+ in those years. We seem to be in a mild summer period, but the winters have become brutally cold with large amounts of snow.
The sensor I'm using only consumes micro amp's, so its not of concern. My main worry is the transmitter, because its consumes so much. Wonder if I increase the bit rate if it will decrease the time its receiving or transmitting. The other issue is if I want to measure the battery voltage and solar voltage. If I am directly powering them from a battery, I will need a voltage divider and a stable voltage reference for the ADC. PICs have a internal voltage reference, but its not accurate enough. The voltage divider presents a problem since it will always draw current.
I've thought of using AAs, but I can't think of any other use for these LiFePO4 batteries, so that's the reason I'm using them. I have 1500mAh's and 3000mAh on hand (2 of each).