Fall isn't here yet - so why are trees changing colors?
The final day of August also brings the last day of meteorological summer.
Unlike astronomical seasons which are based on Earth’s relative position to the sun, meteorological seasons are based on temperature cycles and are much more useful for keeping track of seasonal statistics as well as what they mean for local agriculture. Meteorological summer runs from June 1st to August 31st, with each season lasting 3 full months.
As we wrap up this season and head into meteorological fall starting tomorrow, here’s a recap on the highs, lows, and rain totals of this past summer:
| Observed High | Average High | Observed Low | Average Low | Observed Rainfall | Departure from Normal Rainfall | |
| June | 82.9° | 79.4° | 58.5° | 58.1° | 2.23" | -1.81" |
| July | 84.2° | 82.7° | 64.4° | 62.1° | 5.63" | +1.85" |
| August | 83.9° | 80.8° | 62.8° | 60.5° | 1.99" | -1.77" |
Each month's highs and lows have been consistently warmer than average. This was the 31st warmest summer according to records kept since 1893 based on daytime highs. The coolest month in this category, June, was still warmer than the warmest month on average, July, by just 0.2°.
This year brought the 29th warmest summer based on overnight lows. June's lows were very similar to normal but July and August were both 2.3° warmer than average.
As for rainfall totals, June and August saw a deficit of more than 1.75". Although July was wetter than average by 1.85 inches, it wasn't able to make up for the lack of rainfall during the other 2 summer months. The entire summer season saw a rainfall deficit of 1.73 inches making it the 53rd driest meteorological summer on record.
Even though tomorrow is the first day of meteorological fall, the autumn equinox won't be for another 3 weeks and we won't start seeing fall colors until late September - so why are some trees starting to have leaves turn orange and brown? It's not a sign of an early fall, but instead a tell of drought stress.
When the tree doesn't have enough water, keeping the core healthy is more difficult, so the tree cuts off food to external limbs including branches and leaves to conserve energy. This is what causes the leaves to change color and fall off branches prematurely, but bug infestation and disease can contribute as well.
Leaves shouldn't start changing colors for another few weeks with peak color expected to be reached in October.