Hi,
Are you running it on gas?
Is the burner clean? Sometimes a spider can build a web in the burner area, and that can cut heat output by 1/3 to 3/4! In my buddy's case, it stopped it from working altogether.
You can clean it out with compressed air, and hopefully restore the flame back to full size. It really is not that much bigger than a pilot light.
Have you tried running it on electric? On electric it will put out about 300 - 325 watts or about 900 Btu's. Gas should be 2,200 Btu's per hour. So if it is hot out, I run mine on gas only. Yes even while driving. . .
UNtil then, play it safe and buy ice for the refrigerator, and keep the food under 39F.
Fred.