Every oven is built differently, and that can mean slight temperature variations are present in each model. According to Whirlpool, convection ovens use a fan and exhaust system to circulate hot air evenly, which can help food cook more uniformly. Conventional ovens, meanwhile, use dual heating elements on the top and bottom of the inside of the oven to cook food. This means that if you place your tray of cookies closer to the bottom of the oven, the bottoms will cook first. If the recipe author uses one kind of oven and you own the other, you may need to adjust your baking time.
The weather can also affect your baking — according to Farmer’s Almanac, dry ingredients can absorb moisture from the air on humid days. They also say that recipes may require some extra baking time due to the added moisture, so it may be a good idea to add an extra three to five minutes to your estimated bake time depending on the day. Paying attention to humidity levels is especially important when you are baking something that requires a specific consistency, like pie dough, so that you can avoid a crumbly crust on dry days.