I have a 2007 civic now with 27k miles. I live in the DC commuting area and drive 90 miles a day. Since new, the hybrid system works ok when the weather is cool. As soon as the temp gets above say 85, the pack will start to overheat. The charge and boost indicators will not reach to the top and sometimes stop working altogether. I have brought the car to the dealer several times. They claim it is functioning as designed and quote a page in the manual describing a safety feature that protects the batteries. This appears to be true but I still consider it a defect in that the pack should not be that heat sensitive.
I can start in the morning and everything works fine. If the car sits outside all day and gets hot in the sun, the trouble starts. The hybrid system may work for a minute or two but sometimes not at all. This can be a problem when trying to go at a light and the car wont get out of its own way. After 15 -20 minutes of driving with the AC on high, it will start to function properly.
On a side note, during summer months my MPG drops to 35 - 36 for a tank because of the batteries. Without AC and normal driving I get 38 - 40. The best I have seen for a tank is 42 MPG.
I was thinking of piping an AC vent directly to the pack for cooling. Anyone have the same issue or a solution other than parking in the shade all summer?

 

I know it's not humid but I drove my 2003 HCH a couple days in 90+ degree weather here in CA (we don't get it that often) and I noticed no difference at all...I haven't heard of others having that problem. Then again, it's not that humid here...and D.C. does get a LOT hotter in the summer.

BTW your car is a HCH II (2006 and later), so you may find more help in the other forum:

https://www.greenhybrid.com/discuss/f51/

What color is your car?

 

smhch...try using the Auto A/C vs the reg A/C...you may see better performance and thus, better FE results. I used to use the regular A/C and it would zap the battery pack and a lot of times I would see very little Assist bars.

Your Battery pips will seldom reach the full capacity. Mine typically will sit at 6 pips.

The Auto feature works well because it seems to gauge how much and how hard to work given the humidity in the cabin. Once it optimizes the air in the cabin it doesn't work so hard to keep it there. Whereas the regular A/C just keeps pumping hard, regardless.

I can keep the temp w/ the Auto A/C at 79 in 90+ weather and is still pretty comfortable.

 

Make sure your vents behind the rear seat are clear and do try the auto A/C set at about 80 and see if it performs better. This will keep the pack half cool anyway, and this is important for the life of the pack. H

 

I have a similar concern. I live in Imperial County, CA where summer temperatures average above 115 F. I notice that my hybrid battery tends to drop out relatively quickly during these searing temperatures; and my mpg drops into the 35 to 39 range. I imagine that this has to do with the fact that the a/c has to run constantly to keep the car cool.