1. PROPER FITTING SHOES: Proper width & length fit is far more important that colors or logos. PERIOD.
A. TOO CONFINING: As pertaining to your shoe's length, width, toe box, arch, or heel.This is bad because you have now subjected your foot to being in a vise, while trying to participate a sport that is supposed to deliver enjoyment not pain.
B. TOO LENGTHY: This is bad because you can have fore and aft movement that can cause your foot to act like you are kicking a curb for the duration of your ride - eventually this would become numbing, then sore and may even bruise your toes. ...And... NO... Just cinching the shoe's straps is not the proper solution in this case.
C. TOO VOLUMINOUS: If you scrunch your toes, un-scrunch them. Some riders scrunch up their toes when they ride because the shoe they are wearing is too voluminous - (picture shaking a peanut inside an empty bottle of soda)... Scrunching ultimately this causes a tighter fit in the shoe that can be eliminated by checking your shoe straps/laces from time to time or at worst buying proper fitting shoes (which can be difficult no matter ow long you have been a cyclist with all the crazy sizes and trying to convert them... Trust me no two companies think alike in the size game [if you are a guy and you don't believe me, just ask a woman about her dress shoes]. I find a well established brand, get properly fit, then stick with the same company -I don't care about colors aand logos - Comfort equals enjoyment. BUT this is about scrunching: Verdict here, if you are scrunching your toes... just stop and relax. This is cycling and it is fun for the mind all the way down to your toes - and .. oh yeah... neither is supposed to be numb)
2. TEMPERATURE: Keep 'em warm... keep 'em happy - I know you said this isn't the case, since it was warm where you are.
3. PERSONAL CIRCULATORY ISSUES: I am not a doctor, nor would I give physician's advice, but if my toes went numb I would also try to remember/note if my fingers/finger tips felt numb as well. Sometimes when distracted you may not realize other issues are occurring. THINK - the old joke where the guys says his hand hurts and the 2nd guy says I can hit your foot with a hammer and then you won't feel your hand pain any longer. Silly, I know, but the body works that way at times.
4. FLEX IN YOUR SHOE: If you hammer the down stroke instead of focusing on spinning the 'perfect circle" (or perfect biopace or elliptical thingy) you might get some numbness from that issue. I just thought that if your cleat isn't properly postitioned, could you be doing something that kinda (a far reach here) resembles gripping a mountain bike handlebar. If so then this could be like sleeping with one arm hanging over the bed all night and trying to do pull/chin ups as soon as you wake. It was just a quick final thought, I would like some feedback on this point though.
I had thought to toss something into the arena about crank arm length and trying to reach too far (as can occur when climbing, caving, etc... in regards to one's fingers), but your crotch would probably know more about the error there then your toes ever would.
Thanks for reading my post,
CJ