Aphids generally thrive in temps from the mid 60's to upper 70's. I recently went through an invasion on my kale and collards during a warm spell of upper 70's. Now that the night temps are down in the 30's again they're not so bad. And they reproduce so fast that it takes frequent monitoring to
try to stay ahead of them!
Fortunately, in my garden they seem to bother only the brassicas. I've never seen any on peppers or tomatoes. *keeping fingers crossed*
When you spray, make sure you get under the leaves using either a gloved hand or a stick to lift leaves and spray under them with the other. That will get the most of them but I'm afraid there's no getting all of them and survivors can reproduce so quickly.
Usually I use a hard water spray to knock down as many aphids as possible first, followed by insecticidal soap (sometimes with permethrin mixed in) on/under the leaves and finally a good spray on the ground all around the plants to get those that were knocked off.