There are lots of opinions on this. Most will agree to feed when temps are above 50*. When in doubt, refer to the bag of food and use your best judgement for your situation. The Spring and Fall diet (yes, the link is the one we use) says it is for temps 39-59^... Vibrance says for above 50* ...
When the fish slow down in the cooler weather, so does their ability to properly digest their food, so I follow the 50* rule, more or less. Clearly the bags say we can feed at lower temps than 50^ but unless one has a sterile pond, there are other things in the pond for the fish to eat aside from what we toss them. So the way I look at it is as they become slightly more active and start eating again, they will find what they need in the pond to support their activity. When it looks like they need more, we introduce the Spring and Fall diet first, as it is easier to digest, and then as the water warms, switch to the Vibrance ... as we come into fall, and the water cools, I start mixing the S/F diet with the Vibrance, til they are only getting the S/F diet, and stop feeding when the temp is staying about 50 or less. While they are still pretty active at 50^ there is again plenty of other items in the pond to eat if they are hungry.
Aside from any mechanical filters that may be used on a pond, the pond is also full of helpful bacterias that help with the nitrofication cycle (take care of the fish wastes) ... as the water cools, the helpful bacterias are also lower or less active ... if you dont have enough filtration, the fish waste will lead to water quality issues...
You really should have a thermometer for your pond. There are multi reasons to know your water temps. You can buy ones specificially for ponds for under $10 (or a lot more LOL) or you can go to a discount store and get cutsie ones too for $2 .. Our main pond (thank you for the compliments) has a "real" thermometer ... the pond that just went in has a rubber whale ($2 LOL) and works just fine.
Since you do not have a thermometer, need to ask if you test your water? There's various threads on this forum about water quality...