My "Cold Weather Running Tips" elicited much positive feed back so I will now try to give some tips on hot weather.

In general, hot weather running is a lot more forgiving than cold weather running, as long as you hydrate. Short of heat exhaustion or heat stroke, hot weather running is pretty forgiving. If you follow my tips, you should be able to avoid those two very nasty and possibly fatal conditions and enjoy running a bit more.

Hydration: You need to be hydrated when you run. It is not unusual to lose 3-5 pounds of water weight on an hour long run in the heat. Hydrate through out the day.
Remember, you dehydrate in your sleep and are about 12-32 oz behind right off the bat. When you wake up, drink 8-12 oz of water right then. Try to get down another 12-24 oz in the next 90 mins or before you PT. I usually get about 40 oz in my system before morning PT. Then I do my cals first and have another 4-12 oz before the run.
Immediately begin rehydrating after PT.
If you PT in the afternoon, be sure to keep the water flowing through the day. I drink about 32 oz (one Gatorade bottle) every 90-120 mins through the day.
A good rule of thumb is to piss clear urine or nearly clear urine. If it smells bad, you probably have too much waste and not enough water in your system. If it is bright yellow or orange in color, you are dehydrated. Certain supplements will change the color of urine, so be aware of this.

Heat and Time of Day(assuming no severe warm front rolls in)

Lowest Temp: Just before sunrise in the morning
Highest Temp: mid afternoon, 3:00-6:00pm
Night time: Getting cooler every minute after sundown

Contrary to popular belief, the hottest part of the day is not when the sun is at it's zenith (generally noonish) but between 3:00 and 6:00pm (1500-1800hrs). This is because the ground obsorbs the suns heat and takes time to radiate it back out. The greatest temps result when the sun is still high on the horizon AND the radiating heat has had an opporunity to escape back into the air. Don't believe me? Check out the temperature at ground level-6 inches morning, noon, 4:00pm, last light and just before sunrise. Do the same at chest or head height. You will be amazed at the difference in temperature over time and between the ground height and your head height.
Once the sun goes down, the temperature begins to drop. No more new energy is hitting the ground and the energy stored in the ground continues to radiate back into the air. It will be coolest just before sunrise because this is the maximum time for energy to escape the ground and maximum time with no energy imput from the sun.

Time your runs accordingly to avoid the heat. Often a predawn run is not possible, especially when deployed, due to lack of light or security measures.

A run just after sun up is usually the preferred time. You have good light, no curfews (deployed) and the temp is still mild.

Running after dark. In some areas this works if you have proper reflective gear and enough light to see where you are running. It isn't as cool as predawn but you don't have to get up so early in the morning and this may fit into your duty day better. I ran at Camp Doha, Kuwait, at 10:00pm every night and it worked great.

Running in heat of the day:
Not the brightest move but sometimes it's the only time available. If so, remember to slow down, seek shade and breeze, and hydrate, hydrate, hydrate.

Shade
If possible, run in the shade. This can easily make a difference of 5-10 degrees Ferenheit. Buildings, trees, trucks etc all cast a shadow. If you are running in the heat of the day, especially in a place like Savannah GA, Hurlburt Fld FL, Kuwait or Iraq, these pools of shadow can be life savers.

Wind
The wind offers great cooling properties. Balance the cooling affect of shade againts wind when the structure providing the shade blocks the wind. In open areas without shade, the wind my be your best friend (other than running at cooler time of day and hydration).
Wind from side is best
Wind front on way out and at back on return
Wind back on way out and front on return

Unlike winter where you want the wind at your front on the way out and at your back on the way in, you want the wind to hit you from the side in the summer. This allows cooling through all parts of the run. If you go out with the wind in your face and have it at your back on the return, you will feel much hotter on the return. If you go out with the wind at your back on the way out, you will feel cooler on the return but the wind may serously slow you down and tire you out on the return leg. Balance these two against each other. My technique is to put the wind at my back on the way out but to run slower and turn around a couple of minutes early on the return. I work harder on the return run to overcome the wind resistance but feel cooler due to having the wind in my face.

Running Surface

The type, contour, and color of the running surface makes a huge difference in how much solar energy it reflects, obsorbs, and how freely it radiates this energy back into the air as heat.

Generally, the darker the surface the more it obsorbs light and radiates it back through the day as heat. The lighter the surface the more it reflects light (and heat) immediately. Evaluate this as part of your time of day factor.

Smooth surfaces absorb light and return it as heat more slowly and completely than rough surfaces. Rough or grooved surfaces act as cooling fins (like on the back of your stero amp or the front of your radio) as wind passes over them. They don't build up as much heat over the course of the day and tend to be more even.

examples:
The rails to trails in Savannah GA is white gravel and coral. It is rough and light in color. It reflects light and heat right away and releases heat to the wind quickly. It does not store and radiate much heat during the day so I don't need to consider that as a factor in my run.

The roads around my house are smooth blacktop. The absorbe solar energy all day and slowly radiate it back as heat to the air all day. This means that the roads will be crshingly hot at 4:00 pm and still retain much of this heat after dark. Also, the wind has little cooling effect on the smooth surface so it is not any help. Consequently, I need to run early in the morning to avoid this heat. Late at night would also work but would still be quite hot.

Humidity:
Humidity (moisture in the air) makes a huge difference in how hot it feels to you. The water particles in the air interfere with the winds' cooling effect by slowing down convection (the rate the air particles passing by your hot skin absorbe heat and move it from your body). Humidity works hand in hand with sunlight and radiating heat from the ground to make your life miserable. On it's own, it is not a factor. But with those two factors, it is an important adversary. Humidity changes with fronts more than anything else and while you can check relative humidity on the Weather Channel, you can't predict it that easily. Best to note that the higher the humidity the hotter it will feel. Also note that it effects whether to wear a shirt or not (see clothing). Then use other factors such as time of day and wind to determine where and when to run. A 110 degree day in the low humidity of Arizona leaves you dry and comfortable while a 90 degree day in Destin will leave you hot and drenched.

Clothing:
All you really need are shorts and shoes. Socks are nice for most of us, though not necessary for some people.

Fabric: Coolmax or similar "breathing" fabrics are far superior to cotton which holds heat and water.

Shirt or no shirt?
This is an eternal debate. You have to balance sunburn, windburn and humidity against percieved cooling benefits and restriction of movement.

A wet shirt will cool you down faster than no shirt in most cases.
If wind is primary cooling agent, don't wear a shirt in order to maximize convection cooling (wind blows away your heat). Coolmax may be an exception, especially if sun protection is a factor.

In a dry climate, go shirtless to recieve maximum cooling as the sweat will evaporate quickly and take heat with it.

Some people prefer to wear a a wet or sweaty shirt to achieve evaporative cooling. I find my body heats up the shirt/water/sweat to the point that the heat overcomes the evaporative cooling effect unless I am in a very dry AND very windy environment (Afghanistan, Oklahoma, South Dakota in the summer)

In a high humidity environment, especially one with little wind, a shirt can be good thing. Evaporative cooling is very slow but the water pooled in your shirt from sweat may make you feel cooler anyway. You have to balance this with how much the shirt will restrict movement and how much weight it will gain from the water. Generally, I will wear a shirt in a high humidity environment since there is little to gain by not wearing it and it can protect me from bugs (stick to your skin and hair when shirtless) and sunlight, and also act as a good sweat rag to wipe face and eyes.

Sun protection:
A shirt is the best sun protection, especially a good breathing one made of coolmax fabric.
Sunblock may be necessary in very sunny environments such as Kuwait or Iraq. Try to purchase a sporty or waterproof version that absorbs into your skin and doesn't leave a sticky film. A sticky film will reduce the cooling effect of convection and may be removed by seat anyway.

So here in a nut shell are your hot weather running tips:

Hydrate to point of pissing clear/light yellow

Run in coolest time of day you can (early morning is best)

Run with wind from your side if possible

Use shade if poosible (may be more useful than wind in some environments, especially high humidity/low wind)

Avoid smooth dark surfaces (black top roads) and note these take a long time to cool-may effect time of day you run or route

Clothing needs are minimal (shorts and shoes)
Shirts are always debatable. If available wear coolmax.

Sunscreen may be needed in very harsh climes but should be water proof if worn.

It is possible to run in just about any environment but be smart about it. I have run on blacktop in Kuwait at 4:00 in the afternoon, in August, with a cotton shirt on, avoiding shade just to see if I could. Yes I finished my run but I wouldn't do it again.

Good luck. MC

I'd like to start off by saying, "great post"...LOTS of GREAT advice in there... <img src="/ubbthreads/images/graemlins/notworthy.gif" alt="" />

I can definately say that humidity takes it's toll (along w/ temp., that is) 2dayz ago, I ran 1.5miles in 9:28 (min:sec.) Today, I ran it in 10:50...I noticed you run AFTER your workout...wouldn't that put you running "later" in the day...more heat&humidity...I know there's probably a good reason for this...I just don't see it.

Gonnabemed,
Glad you liked the post and are applying it along with a good dose of critical thinking. If I only have one time block for PT (which is normally the case) I want to do cals and run. Since I am a better at running than cals, I do my cals while I am fresh so that I can get max reps. The cals do degrade my run but not as much as my run degrades my cals. Also, I am more laid back about my runs because I have more experience at it. It is much easier for me to guage how much my cals have affected my run than the other way around. Then I can take appropriate action (run harder or just accept a slower pace, depending on the type of work out and my training goals). I know I am more likely to work harder to get my run where it needs to be than I am to get my cals where they need to be once I get tired.
When I run before I cal, my numbers drop quite a bit and it really aggrevates me. I KNOW why the numbers are lower but it still leaves me FEELING defeated so I avoid doing the run first to make myself feel better about my PT. I know it's a mind game but at 36 years old, you start playing games just to keep yourself working out.
Sometimes I will shake things up and run first, just to break out of a plateau on cals or running.
Also, if you read my posts on crap and running, you'll note my advice to do cals (especially ab work) before running. This allows you to get more (hopefully ALL) of the fecal matter out of your system before the run. This is especially true in the morning, when I normally PT.

Also, though I never came right out and said it in my Hot Weather Running Tips, I love running in hot weather and look at it as a challenge. I started running at 3:30 every afternoon in the summer during High School because it was the hottest, most miserable part of the day. Most of my runs were on black top roads, amplifying the heat but I figured this would just make me stronger. Finally, if I really wanted a challenge, I would run on farm roads closely flanked by cornfields so their was little or no breeze to cool me down. All this was intended to make Cross Country Practice and Races easier. (both normally started at 3:30 until late in the Season when meets would be held on Saturday mornings). After 4 years of High School and 3 years of College running, it just got to be a matter of pride that I could run strong in the heat. Today, 14 years after college, I am way out of shape (my last eval 3 mile was 19:34 compared to a college time of 15:30) but just can't seem to let go of that pride. So, I run in the afternoon, on black top roads, pushing the pace, just to see if I still have some of that mental toughness left. As you get older, you don't always get wiser.

So, the short answer is
1) I do cals before I run because I suck at cals
2) I do cals before I run to get all the crap out
3) I run in the heat of the day because of foolish pride

Question for you, it was about 72F & 85% Humidity here tonight,I work nights so I usually do my running between 0200-5. Friday I did a 3k perfectly normal unsure of the current humidity, and today i was going to do 3miles. Well about a 1.5 into my running I just felt like I couldn't breath(not short of breath!)like I was unable to deliver proper o2 to my musles, normally I have no issues with this.

With such a high humiditly Level do you believe it would be better to do sprints instead of long distance, I did a couple 1/8mile sprints with less difficulty, any thoughts on how to make the most of my work out

I wouldn't change my workout schedule from speed work to easy runs or vice versa due to humididty or temp. I'd adjust the time of day instead. If you can't do that, slow your pace on the easy days and the recovery run of your speed workout.
Your issue may have nothing to do with humidity, though high humidity does leave you feeling like you are breathing through a wet towel sometimes. Look for signs of over training or maybe short term lack of sleep or some other fatigue factor.

Funny you would say time, haha it was about 3am. I think you may be right on the over trainning and lack of sleep. (night shift)

Thats pretty much how I felt, like I had wet towel over my head. I took about a 5min break then went to try and finish the 1.5 I had left, tried the slower pace did about .5 and was right back to where I had stopped before. Took another 5min break then did athe 4 sprints w/2min breaks

Due to a new shift (0400 - 1400) I had to change the time of day that I run. I used to run a 1530, when it's 473 degrees. Today I ran at 0600 and I was amazed at how much further I was able to run. I was flying this morning, felt like I could have ran all day. Before I knew it was 4 miles into the run and still maintaining pace.

It may seem obvious that you can run longer in cooler temps but the difference was drastic. My .02

Mason