So, I've heard Prius gets better mileage in warmer weather. I live in Phoenix though, where highs regularly exceed 110 fahrenheit in the summer. At that point, doesn't mileage start to decrease (either by virtue of A/C working overtime, or just decreased battery performance)?
Art_Vandelay -The Prius Hybrid Synergy Drive delivers the best fuel economy in warmer climates, like Deep-South Dixieland, Florida, Hawaii, AZ, NM, NV, SoCal and TX, at the time during the year when the daytime outside ambient air temperatures (OATs) are in the low 60s to low 80s (Fahrenheit) range most of the time. Warm outside ambient air temperatures serve to shorten the duration of the warm-up period and length of the "thirsty" Initial Start/Restart “Rich-Burn” Mode of fuel consumption. Once the OATs drop below or rise above this “Happy Hybrid” operating range, air conditioner or heater use works to lower running MPG. Of course, this “Hit” to MPG in Hot-Cold operating environs is true for conventional, ICE-Only powered vehicles.
I have no trouble getting 47, its certainly far better than in freezing temps. Using ECO mode helps. The AC isn't as hard on MPG as some folks around here would have you believe.
I am going to jump in here and urge you to get lower MPG. The same A/C that keeps YOU cool and comfortable is cooling your batteries and keeping them comfortable and longer lasting. Do not skimp on A/C. (Frequently, it is not the heat, it is the humidity. I was a fry cook in Phoenix, it was the heat)
...and the Devil sighed, "...yes, but it's a HUMID heat during our monsoon Hades season..." (wink,wink)
Usually only gets to 95 here in summer, but I forget if that is the heat and/or the humidity. Average High/Low Temperatures for KGWO | Weather Underground
On Guam (middle of Pacific ocean) our tongue-in-cheek motto was: "...in God we trust, on Guam we RUST..."
