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Look for cooler, wetter weather with coming arrival of autumn

Thu., Sept. 19, 2013

It’s been a hot summer in the Inland Northwest.

Our mid-September heat ended Sunday night with the storm that swept in, bringing showers and cooler weather for the rest of the week.

I’m fairly confident that we’ve seen the last of the 90-degree or warmer days. There were 29 days at the Spokane International Airport with high temperatures at or above 90 degrees – one in June, 14 in July (including a 10-day stretch starting July 17), eight in August and six in September (including a five-day stretch starting Sept. 11).

The record for number of days at or above 90 is 39, set in 1958. In 1998, there were 38 such days.

And though it was hot this summer, we never hit 100 degrees. The hottest day was July 1 with a high of 99.

Fall looks wetter and cooler thanks to the cooler La Niña sea-surface temperature pattern in the Pacific Ocean.

Our area has cooled down just in time for the beginning of fall, also called the autumnal equinox, at 1:44 p.m. Sunday.

In school, most of us learned that the Earth has seasons because it is tilted on its axis by approximately 23.5 degrees. In our summer, the Northern Hemisphere is tilted toward the sun, allowing us to receive more direct solar radiation and hotter weather. In our winter, the Northern Hemisphere is tilted away from the sun. This is why we have shorter days and a lower sun angle. Distance from the sun has nothing to do with seasonal changes in temperature, as we are actually closer to the sun during our cold season.

On the equinoxes, every point on earth has about 12 hours of day and night. The reasons the times are not exactly 12 hours apart on the first day of fall are complex. Our location in a particular time zone, elevation and the fact that the sun is not a singular point in space are some of the explanations. In Spokane, we will have 12 hours, 10 minutes of daylight on Sunday. Wednesday we’ll have 12 hours of daylight – sunrise is at 6:41 am and sunset is at 6:41 pm.

If you have any questions or comments, you can contact Randy Mann at wxmann, or go to www.longrange for additional information.

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