Why Do I Feel Tired and Dizzy Cycling in Hot Weather?

Question: I am 68 and have been a recreational cyclist for the better part of the last 40 years. In my 30s I’d ride 60 miles in 90-degree heat (hey, there’s a breeze), no problem. About 4-5 years ago, riding in the heat became intolerable. If it’s high 80s or higher, even after as little as 10-15 miles, I not only get dizzy but lose muscle strength so that I can’t hold up the bike, let alone pedal.

Usually, I can walk the bike, but sometimes I can’t even do that. I have to sit until I feel better and then try to ride again, sometimes several times until I get home. I know as you age, your cooling system doesn’t work as well and I’ve never been good at hydrating sufficiently. Is it just a question of drinking more, or is there something else I can do? – Ellen S

RBR Replies: First off, I’d strongly recommend checking with your doctor about these symptoms. They could indicate an underlying health issue that needs attention. Be sure to discuss the dizziness and muscle weakness you’re experiencing in the heat. Your doctor may want to look into potential causes like dehydration, electrolyte imbalances, cardiovascular changes, medication side effects, or something else.

Now, let’s talk cycling. Heat tolerance definitely decreases as we age, but there are several strategies you can use to stay more comfortable on hot rides:

Hydration is crucial. Start drinking extra water the morning before a hot ride. During the ride, aim for at least one large water bottle per hour, more if it’s extremely hot or humid. Adding electrolytes to your water can help replace what you lose through sweat. If you’re worried about overcompensating and drinking too much, the first signs of over-hydration are that you’ll need to stop and pee a lot and your urine is very clear.

Timing can make a big difference. Try to ride earlier in the morning or later in the evening when temperatures are cooler. Not only is it more comfortable, but you’ll likely have less traffic to contend with too.

Dress for success with lightweight, breathable clothing in light colors. Look for jerseys with mesh panels for extra ventilation. A well-ventilated helmet can help keep your head cooler too.

Give yourself time to acclimatize to the heat. Start with shorter, easier rides and gradually increase your time and intensity as your body adapts. Consistent exposure to hot weather riding will help you tolerate it better over time.

During your ride, use cooling techniques like wetting your jersey or bandana at water stops. Take breaks in the shade when needed. You might even consider freezing your water bottles the night before – they’ll thaw as you ride but stay colder longer.

Most importantly, listen to your body. If you start feeling dizzy or weak, that’s your cue to take a break, find some shade, and cool down. Don’t push through those warning signs – it’s not worth the risk.

With some adjustments to your riding habits, you should be able to extend your comfort zone in the heat. But remember, there’s no shame in cutting a ride short or rescheduling for a cooler day if conditions are too extreme. The goal is to keep cycling enjoyable and safe for the long haul.

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16 Comments

  1. It comes with age! Up through my early 60s I could ride in just about any summer temperature (taking many fluids from a hydro pack and electrolyte caps). One bad day, past age 65 on a 100+ mile ride on a hot Kentucky day, I was feeling a bit queezy. I blamed something I’d eaten too much of at a rest stop. NOPE! For me, the nausea was my first sign of heat exhaustion. The second sigh was slowed reaction times. The bruises from the resulting crash were quite painful for a couple of weeks! SO, past a certain age (it varies), I would say everyone suddenly reaches a point where they are limited by the combination of heat and distance.

  2. I”ve been experiencing the same issues this summer. I never had a problem with riding in the NJ summer weather until this year. Not sure if it’s normal aging, the combination of drugs that I’m now taking (two are new from last year) or some combination of the two. But I have noticed that humidity tends to be more of a factor than heat. Not totally sure why, but I definitely feel and ride better when the RH is on the lower side for NJ (below 70%). Not sure if anyone else has noticed the impact of humidity more than temp.

  3. I was having the same issue with getting dizzy riding in the heat. Initially, my doctor thought it was due to medications for hypertension. After I got dizzy after only 10 minutes putting up shelves in my shed, I thought it must be something else. A CBC showed I had low hemoglobin. Ultimately, the source was a hiatal hernia with erosions on the surface. Iron supplements have largely fixed. I still have a hard cut off of 90 degrees and I don’t ride.

  4. I just felt I had to comment on this one! I’m 76 and live in Texas. For years I rode a weekly 30 mile high speed group ride in 100 degree temps and always came home with a roaring headache. I realized that my water intake on most days was very little. So I upped it…drinking about 100 oz on a ride. This didn’t help a lot, but was better. Today, I drink water through out the day, probably something like the recommened. But too, I’m now using a fluid replacement drink during my rides and immediately after. Water alone is important. But that expensive additive is well worth the price if you are gonna sweat a gallon. Too…why do others wear dark jerseys? And, when you get my age and your skin begins to wrinkle…consider DaBrim or something similar. I may look goofy, but hey, younster, that skin cancer or all those wrinkles…their there for the rest of your life.

    1. I’ll just add that in taking my BP after a ride, even as late as two hours, it was exceptionally low. I wasn’t experiencing dizzy, but coming close with top BP and HR almost equal. Summer is a bitch with the heat, but ride early and limit your exersion and time. Cooler weather is coming, even if you won’t ever be young again.

  5. Wind chill occurs due to sweat evaporating. It is hard for it to be too hot for electric biking.

    Oddly enough this makes sweating and dehydration actually WORSE with electric biking. I never get even damp because I’m in a 20 to 30 mile per hour wind all the time. Doesn’t matter the heat. Doesn’t matter what percent I’m putting into the power. The sweat evaporates really fast.

    This means I get dehydrated MORE and notice it not at at all until I keel over. Worse than keeling over? My thinking gets just a bit off well before I have other symptoms and well before I feel faint. This impairs judgement on what is ok on electric biking and this is more dangerous than the actual vascular effects.

  6. I had a recent experience in which after a ride in hot weather I had difficulty getting up the steps to my house and even standing up in the shower — none of which had ever given me trouble before. It turned out that I had lost 3 1/2 pounds on the ride, obviously water weight due to sweating, and I was dehydrated. I had lost sight of something I learned many years ago: drink before you’re thirsty. Since that ride I’ve followed the drinking advice and have not had any problems since. (BTW, this happened a few weeks before my 65th birthday.)

  7. For me a CamelBak and a cooling towel around my neck are lifesavers riding in the Phoenix summers. I put ice-water and 3-4 salt tablets in the 50 oz camelbak. Having the hose dangling in front of me reminds me to drink often and is safer in a paceline than reaching for a bottle. I also carry 2 bottles of ice-water and use one to wet the cooling towel regularly. At stops, I drink a small bottle of pickle juice, or packet of maple syrup. Starting rides early before sunrise and keeping the distance below 40 miles in the summer is a no-brainer. So far I haven’t seriously overheated on a ride using this method.

  8. With a lot of long distance riding in hot/humid weather, I’ve developed the following rule of thumb for water intake: an ounce per mile for “normal” conditions and up to 1.5 oz. per mile on challenging days. That means 5 quarts (nearly 5 liters) of liquids on a century, and I still lose weight. Also, not that adequate hydration doesn’t mean “clear” urine, it means “light colored” urine. Even dark colored urine can be clear. I also have learned to keep my electrolytes separated from my water. Then I can use my water to pour over my body, clean my hands after a repair, or even clean road rash. I add roughly a teaspoon of salt to my cookies and mixed nuts for long rides.

  9. I echo the advice to see a doctor to find out if the symptoms are the result of a medical issue. I have thyroid issues and experienced similar symptoms on a ride a few years ago. I became dizzy and had to stop because I could barely turn the pedals. It was not an especially hot day (mid 80’s) but it was the first warm day following a cold spring so I was not acclimated. Now that my medication has been dialed in, I have no problem riding in the heat.

  10. I’m 80 and ride about 8,000 miles a year mostly in the Chicago Metro area. Twice in the last two years I have reached a condition of lightheadedness that caused me concern. On one occasion, I opted to be sagged in, on the other I was close to home and took the short route the rest of the way. On both occasions I was somewhat dehydrated, but more significantly., I was undernourished. I rode further, harder and in hotter weather than I anticipated. Both times I hydrated with chocolate milk and Coca-Cola post ride. In both cases I had something to eat and continued to hydrate. I felt recovered within about two hours. I have subsequently been checked by a cardiologist and monitor my resting heart rate and BP. RHR remained elevated for about a day. while BP was slightly lower than normal.

    I’m convinced this was a low blood sugar condition (another indicator, I drank two bottles of water in both cases but continued to be thirsty until getting sugar back into my system.

  11. CANNOT emphasize enough the need to get a medical eval for those symptoms!!!!!. Two of my fellow club riders recently had similar issues and initially blew it off as heat related. One turned out to have serious coronary disease (with NO chest pains/pressures!), had stents, & is now back to riding well. Another, although getting routine checkups, unfortunately ignored his increasing fatigue and did not get checked for them. He tragically passed away on a ride 🙁
    Listen to your body. Being tough does NOT being being foolish.

  12. Iwas first diagnosed with Atrial Fibrillation in 2016 and had Ablation in 2017, Afib episodes were absent until a ride in 2022 when I failed to hydrate adequately on a 50 miler. The spell happens within the last 2 miles and I ended up walking the bike to the car. Since then, Im very religious with water intake.

  13. I had this issue in heat for a couple of years, and it was severe as the weather warmed up as well, it was caused by my prescribed statin drugs for cholesterol. Even though I had been taking the same statin for ten years, it suddenly became an issue. Talk to your doctor about temporarily stopping or changing statin drugs if you are on them.

  14. I am 73 and have ridden many years in all Temps. Two years ago, my MD started me on blood pressure medication (losarten). When I mentioned the issue to him, he suggested not taking my dose on hot, humid days with long ride plans. You are sure to be somewhat dehydrated, and the meds will cause your BP to drop very low.

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