Expert: Dave Dombek - 9/4/2002

Question
Is there a general rule of meteorology that explains the relationship between  falling air temp. and water temp.? For instance, in the fall time of the year in southern Michigan, air temp. begins to decline in mid to late september. Mid 70 to 80 during the day and 55-65 at nite; under these conditions water temp. still remains 75-80. At what point does water temp. start to decline with falling air temps.?
2. Can you use historical air temps to predict weather patterns in the current year?

Answer
James,
As a general rule of thumb, it takes longer to warm up water, especially a large body of water like the Great Lakes, than it does to warm up land. On the opposite end, it takes longer for the water to cool than land. There is usually about a one month lag between the peak of the normal temperature curve (in Michigan it is late July and the first few days of August) and the peak of the water temperature curve, which occurs in late August and the first few days of September. From this point on through the fall, air temperatures and water temperatures will cool, but there will still be that lag. That is why it is harder to get it to snow right near Lake Michigan in early December than it is in the middle of March. The normal tmeperatures reach the bottom in late January and the first day or two of February, while the coldest lake water temperatures are not reached until about a month later than that.
For question #2, that is beyond my field of expertise.
Hopefully this helped you out. If so, please close out the question and give me a rating. Thanks!

Sincerely,

Dave Dombek
Expert Senior Meteorologist
AccuWeather.com