The signs of August are certain. Back-to-school sales are on. The evenings are filled with sounds of chirping insects. Grasshoppers bounce along the gravel in the afternoon heat. Motorcycles are rumbling throughout western South Dakota and eastern Wyoming a couple of hours after sunrise.

During the next 45 days, we'll see summer hang on for all she's worth, and then, we'll have that one defining morning when we'll wake up and it will feel like autumn.

The summer blast furnace is belching one more round of 100-degree heat this week and then the readings in the 80s and 90s will be more typical.

There may be one more day when the temperature threatens to climb toward 110 degrees this week - except in the Badlands, where there may be two or three days left for temperatures to sneak up close to 110.

For most of us, other than a few stray days when the thermometer will register just over 100 degrees, I think it is safe to say the last of the hot days will be this week.

The summer monsoon season finally set in across the Desert Southwest two weeks ago, and the moisture will surge northward across the Great Basin.

From there, it will arc eastward toward us. We will certainly see the high altitude clouds blow in from the West and Southwest off the tops of Rocky Mountain thunderstorms on a regular basis from now through the end of the month.

Spotty areas will get beneficial late summer rains as late afternoon and evening thunderstorms flare up in the monsoon flow of tropical moisture.

The best chance of rain will be across South Dakota's southern tier of counties, over much of Nebraska and southeast Wyoming.

Northeast Wyoming, eastern Montana, western North Dakota and northwest South Dakota will see only random thunderstorms through mid-August with only a few lucky souls receiving rain of any significance.

Recent puddle-producing rains have boosted the insect population, particularly mosquitoes.

Some of those nasty blood-sucking creatures carry the West Nile virus. New, preliminary research says that the species most likely to carry West Nile are out en masse between the hours of 10 p.m. and midnight.

That is the most likely time to be poked. Bug sprays containing deet seem to be the best way to prevent a bite, but that's not a sure bet, either.

If you are here on vacation, the good news is that western South Dakota has a lot fewer mosquitoes than areas to the east - much fewer than east of the Missouri River.

I am glad that I live in a part of the world where I can count on one hand the number of mosquitoes I encounter in one week.

It is not mentioned in the travel brochures, but people who spend the bulk of their vacation on the west side of South Dakota slap themselves less and have far fewer bug-bite welts than vacationers on the east side of the state. All kidding aside, West Nile virus is a serious threat, and you need to be aware of the danger of mosquito bites.

Chris Orr is a Certified Consulting Meteorologist in private practice, morning meteorologist at KNBN-TV NewsCenter1 and can be heard on the radio show Live With Jim Thompson on Wednesdays. E-mail him at weather@rapidwx.com or go to www.rapidwx.com