Archive for September, 2007

Red Flag Warning

Sunday, September 30th, 2007


Did you happen to see the red flag warning banner on our web page this afternoon? This indicates conditions are dry and windy enough to increase the fire danger. More specifically the NWS definition:

A fire weather watch or red flag warning is issued when the combination of dry fuels and weather conditions support extreme fire danger. These products are written for land and fire managers to highlight the increased fire danger.

Each NWS office creates local criteria for fire weather watches and red flag warnings. The criteria for northern Illinois and northwest Indiana include:

  1. Sustained 20 foot winds of 20 mph or higher.
  2. Afternoon relative humidity less than 25%.
  3. 10 hour fuel moisture at 8% or less for one day.

A fire weather watch is issued up to 72 hours before the above conditions are expected to occur.

A red flag warning is issued when the conditions above are expected to occur or are occurring within the next 24 hours.

It’s hard to believe how quickly conditions changed from extremely wet in August to extremely dry!

National Weather Service Chicago Open House Oct 6, 2007

Thursday, September 27th, 2007

The National Weather Service Chicago Forecast Office located in Romeoville, IL will be having an open house on Saturday Oct 6th from 9 AM to 3 PM. Stop by to see how forecasts and warnings are created for northern IL and northwest IN.  Detailed information can be found here.  Pre-registration is not required.

Autumnal Equinox

Saturday, September 22nd, 2007


The autumnal equinox will occur at 4:51 AM CDT on Sunday Sep 23, 2007. The equinox is defined as when the sun is observed directly over the earth’s equator. The sun angle will continue to sink further south each day as our total hours of daylight continue to diminish.

Patchy Frost Possible Overnight

Friday, September 14th, 2007

frostIf winds subside, patchy frost is possible overnight. Did you know that frost can form even when the temperature reading is above freezing? How is this possible? Many thermometers are located around 3 to 5 feet above the ground and often temperatures at or just above the surface on clear cool nights can be colder than those at the height of the thermometer. Water vapor that comes into contact with the cold surfaces freezes and produces what we refer to as frost. It would be interesting to compare temps just above the surface with the standard reporting height to watch the variations.

A Taste of Autumn

Monday, September 10th, 2007

Cold fronts  sweeping across the region this week will result in some of the coolest air experienced since spring.  Low temps should dip to the low 40’s early Tuesday morning. A brief warmup will allow temps to climb again to around 80 on Thursday before the next front moves in and brings with it even colder temperatures. Lows on Friday morning could be in the upper 30’s. Time to give the air conditioners a rest.


Saturday, September 8th, 2007

Record rainfall in August has produced one of the largest mosquito populations that we have experienced since moving here. It seems like the minute you venture outdoors you are a target — day or night. Unfortunately they will be around until the first frost which occurs on average here around mid October. Keep that repellent handy!

August 2007 Climate Summary

Sunday, September 2nd, 2007

Here are a few stats for August 2007:

Max temperature was 91.5 on 8/7.
Min temperature was 51.9 on 8/31.
Average temp was 74.3.

Total rainfall for August was 11.60 (!) inches. Normal rainfall is around 4.3 inches. The maximum 24 hr rainfall was 5.01 inches on 8/23.