We issued our official summer forecast earlier this evening. Just a refresher on how we go about our seasonal forecasts. We pick one or two unusual monthly numbers for the current season and compare them to past years.  April was key to this year’s summer forecast.  It was unusually warm this April (3^rd warmest) and there was little snow (just a trace).  Here is what we found based on these numbers.

When looking at the past ten warmest Aprils, 7 out of the 10 following summers were warmer than normal. There also seemed to be a connection between how warm it was in April and the number of 90 degree days. The chances of going above the ‘normal’ number of 90 degree days (which is 8) was only 27% when April was cool. When April temperatures were normal or above normal your odds went above 50% (57% and 56% respectively) but when you narrowed the warm Aprils to just the top ten warmest April the chances for more 90 degree weather shot up to 80%!

Now on to the April snow. When we had .1” of snow or less in April in the past, 8 out of the 12 summers that followed were above normal in temperature. You might think that shouldn’t the warmest Aprils also be the least snowy April?. That wasn’t the case.  Only 2 years (1952, 1955) made both lists..  One other note about temperatures: In those 12 years with little or no April snow were the 3 warmest summers in Syracuse history (2005, 1949, 1955).  Here’s another 90 degree connection: 7 out of 12 of these years had at least 18 days when the temperature exceeded 90 degrees.

Normally when we do a summer forecast we don’t find much of a signal for wet or dry weather. I think the reason is the more scattered nature of the precipitation. One spot can get 2” of rain from a thunderstorm while 10 miles away just a trace of rain falls. This time around we did find a signal for a drier than normal summer.  7 out 10 summers following warm Aprils were drier than normal.

So to sum up, it looks a warmer and drier than normal summer. We are figuring on at least ten 90 degree days.  I’ll throw one more nugget that is not part of the official forecast. It’s my belief that the heat will start early in the summer season since I found the strongest signal of warmth for June.

One additional thing I looked at for this summer forecast was how these past Septembers ended up. We all remember how nice (but dry) the late summer/early fall was last year so I thought we could look to see if summer weather would linger through September.  After all, Fall doesn’t officially start until September 21^st.

Using years with little snow in April as our baseline, we found that 8 out of those 12 years had warmer than normal Septembers and the chances for 90 degrees that late into the season increased as well.

Now my ‘buyer beware’ fine print statement. As you look at all this data keep in mind we are still playing percentages. No two summers or winters are exactly alike. Whenever we see what looks like a strong signal the percentage of warmer than normal summers is 70 or 75%.  That means there are 25-30% that are near or below normal in temperature. It’s not all black and white when making the seasonal forecast there is a certain grey area. We’ll see how the next 3 or 4 months pan out. If you have any questions I’ll try my best to answer them.