That's indeed what I meant, because the summary I found seemed to include ice core data and tree rings as well as the (100 and some year old) weather service data.

Unfortunately, I can't find that summary anymore, so we'll just assume I made the whole thing up, and have a look at the USA Today summary here. :)

As mentioned above, replacing lost electrolytes is important. I recommend drinking at least one Gatorade type drink (with sodium and potassium in ingredients) about the mid-point of your day's ride.

Drink plenty of water as mentioned - make sure you enough - better to carry extra than worry about conserving it. On occasions I found that no matter how much water i gulped down i never quenched my thirst, which i've since found out is not because i needed fluid but because i needed to replace lost salts. so energy drinks are one option if available, or make up your own. otherwise put salt on your dinner and sugar in your tea/coffee or drink something like coke.

wearing a cap really helps and make sure you don't get burned - sunscreen or cover up with a light, loose top.

don't cycle middle of the day. either get up earlier (you could start before sunrise) or rest midday and continue in the evening. Always stop in the shade when you can find it, even if it's just for a few minutes.

My touring season (and hiking season) begins in mid-September. Summer is for getting home projects done, hittin' the gym, a few short rides, generally relaxing... and looking forward to vacation time!

Night Riding
 

A good lighting rig weighs a lot less than extra water. If you like night riding, I would recommend timing your daily arrival for 7-9am. Particularly on days you expect 6 or more hours of riding. Sleeping somewhere between 4pm and midnight is nice too.