I can confirm that the battery climate is the same here in central France.
Battery status of my 2010 15" MacBook Pro i5 says "Service Battery" and battery life starts from 3 to 4 hours. It used to be 7-8 hours. It drains quicker than before.
I've done the SMC reset procedure described earlier, and reset the Energy Saver settings to default.
Model Name: MacBook Pro
Model Identifier: MacBookPro6,2
Processor Name: Intel Core i5
Processor Speed: 2.4 GHz
Number of Processors: 1
Total Number of Cores: 2
L2 Cache (per Core): 256 KB
L3 Cache: 3 MB
Memory: 8 GB
Processor Interconnect Speed: 4.8 GT/s
Boot ROM Version: MBP61.0057.B0F
SMC Version (system): 1.58f16
Serial Number (system): ?
Hardware UUID: 25534838-2CBB-599D-9A9C-D59D210D83D2
Sudden Motion Sensor:
State: Enabled