Despite a relatively cool July —the mean July temperature was actually cooler than the mean June Temperature, both here in Lawrenceville and in Atlanta— it looks like August is going to be our hottest month of the year.

The short range, medium range, and long range forecasts are all calling for warmer than normal temperatures, and it looks like we may not get much rain to help out, at least until the middle of the month.

Temperatures will be approaching the 100 degree mark all this week in North Georgia. To make things worse, we’ll likely be seeing high dew points as well. That means that the humidity will be approaching the unbearable range. Take a look at the forecast dew points in Georgia for 2 PM Thursday:

If this forecast validates, we’ll see the heat index above 105 degrees, the danger level, several times this week.

Ultimately, it’s the moisture in the air that determines how we feel when we go outside. Although relative humidity is the measurement most people use to measure moisture content, the dew point temperature can provide a better measure of how uncomfortable conditions are. When the dew point rises to near 70 or above, most people are unlikely to want to be outside for very long.

The heat index also measures the apparent temperature. For more detail, take a look at this table showing the relationship between relative humidity, temperature, heat index, and dew point.

The reversal from the cool and wet July conditions to the hot and dry conditions for August isn’t going to do much to help the drought conditions in Georgia. Over the last month, the drought levels in Georgia haven’t changed very much. While the rain has kept lawns green in the short term, we will see a quick return to brown lawns without more rainfall.

As I’ve said before, tropical weather will probably be the key to breaking the drought. Despite the relatively quiet season so far, the latest forecast by Dr. Gray at Colorado State University is still calling for an above average hurricane season. The researchers are predicting 15 tropical storms for the season, down 2 from their May forecast, and eight hurricanes, down from nine in May. There’s also an above average chance of a major hurricane striking the US coast.

You’ve undoubtedly heard about the extreme heat in much of the western part of the United States. Here are some high temperature readings from Friday, July 6th:

Bullhead City, Arizona 118 degrees
Phoenix, Arizona 113 (Not a record)
Tucson, Arizona 107 (Not a record)
Boise Idaho 105 (new record, breaking previous 101 degrees in 1985)
Bozeman, Montana 106 (Record)
Billings, Montana 104 (Record)
Glasgow, Montana 102 (Not a record high)
Missoula, Montana 107 (Record)
Elko Nevada 104 (Breaking old high temperature record of 102, set in 1913)
Las Vegas, Nevada 115 (Ties record set in 1989; with a high of 113 predicted for 7/7/07, I wonder if the gamblers who decided to visit Las Vegas on the luckiest day of the century are really feeling lucky?)
Reno, Nevada 99 (Not a record)
Ontario, Oregon 106 (Records set on the 5th and the 6th)
Salt Lake City, Utah 103 (Breaks record of 102 degrees in 1973)
Hanford, Washington 102 (Not a record)

Typically this time of year, the national daily high temperature is set in Death Valley California, and so it was again yesterday, with 129 degrees, 12 degrees above normal.

While the excessive daytime temperatures are in many cases warmer than the Atlanta area has ever seen, keep in mind that they are accompanied by extremely low humidity. For example at the time that Las Vegas reached 115 degrees yesterday, the dewpoint was 28 degrees, and the relative humidity was 5%.

Additional records for the highest low temperature are being broken as well. In St. George, Utah yesterday, the low got down to 92 degrees, breaking the all time low minimum temperature record set back in 1970.

Next week’s weather could get interesting, as the heat wave moves east. Because of the persistent low pressure system dumping rain on the southern plains, the extreme temperatures won’t reach Atlanta. But, high temperatures in the upper 90s are likely to make New York City miserable early next week. High temperatures of 98 in Boston, 96 in Chicago, and 98 in Washington, DC are going to affect a lot more people than the records being set out west. Look for the weather to dominate the headlines again next week.