Hot weather means less power through that cord.

Yes, temperature directly affects how much current an extension cord can safely carry. Higher temps = less capacity.

Here’s the short version: copper wire has more resistance when it’s hot. More resistance means more heat, which means the cord can overheat faster if you’re already pushing its limit. Most cords are rated at 60°C ambient (about 140°F). In direct sun on a summer day, the ground can easily hit 120°F — that’s close enough to derate the wire by 10-15 percent.

Practically? Don’t run a space heater or a miter saw on a 100-foot cord in July if you can help it. If you must, go up a gauge. A 14-gauge cord at 90°F air temp handles less than its nameplate rating. The National Electrical Code has tables for this, but for everyday use: if the cord feels warm to the touch when running something, it’s too small or too long for the job.

Heat plus load plus length is a triple threat. Get a thicker cord than you think you need.