Peoria, Ill. – The countdown to Halloween is on, and while we are still more than a week out, we are starting to get an idea as to what the weather pattern will look like at the end of the month.
The weather over the past few weeks has been rather active thanks to a progressive weather pattern. This often results in fluctuating temperatures, breezy conditions and multiple shots or rain throughout the week. However, the pattern looks to change at the end of the month.
The jet stream is expected to become more amplified through the end of the month as blocking ridges develop across the north Atlantic and the north Pacific Oceans. These ridges will send warmer temperature poleward which then forces colder air from Canada to move south, a product of a weakening polar vortex.
This weakening of the polar vortex is often seen in the Arctic Oscillation (AO), a short term climate pattern that changes every couple of weeks. The phases of the AO often influence temperature trends across the U.S. When the AO is in a positive phase, temperatures are often warmer than average but when it dips into a negative phase, colder temperatures can be expected. During the winter months, a negative AO typically means a blast of arctic air is going to impact the U.S.
Looking at the Arctic Oscillation Index the AO has been slightly negative. This has resulted near to below-average temperatures in Central Illinois. However, as we get closer to Halloween, the AO is expected to turn sharply negative which is a strong signal for much colder air moving into the area.
Given that Halloween is still more than a week out, its too soon to get into any specifics. That said we can see that the overall trend favors below-average temperatures and near average precipitation between October 29th and November 4th. It’s not clear whether or not snow will make an appearance through the first week of November, but it is looking more and more likely that Halloween will be a chilly one this year!
Peoria Halloween Stats
Normal High: 59°
Record High: 85° in 1950
Record Low: 35° in 1917
Average Precip: 0.10″
Wettest: 1.69″ in 1994