This is actually a bit on the high side. AC vent temperature should ideally be around 4-5 Celsius. I think that first you should visually inspect the condenser and see if its damaged or not. Sometimes, the fins are broken by road debris and even insects(they are extremely fragile) and this affects AC performance.
If the condenser looks in OK condition, try to clean it using mixture of vinegar/water (use spray-bottle and let it sit for some time, and then rinse with water). This step worked for me when I was facing the same issue in my City PT a few years back, vent temp was at 9 degrees, but after this procedure it came down to 5 degrees.
If nothing works, then you are probably low on AC refrigerant. Check this, and if this diagnosis is correct, use c.420-430 grams of high quality R134a refrigerant and refill your AC system.
Also, I would add that all Honda A/Cs I've experienced are generally a bit on the weaker side as compared to Toyota A/Cs. Toyota A/Cs will cool the cabin down to lower than 18 Celsius at noon on a sunny day(tested on Altis 1.6). While Honda's A/C will never go below 20 Celsius in such conditions(City 1.5 PT). And bear in mind, I'm quoting ambient cabin temp not vent temp. If you are used to Toyota cars, then you will have to get used to lower-performing A/Cs in Hondas unfortunately.
