is it okay to have only water in my radiator and reservoir-no coolant?

ONLY FOR LITTLE WHILE ,IF COOLANT IS NOT AVAILABLE ,CHECK FOR WATER DILUTION IN COOLANT , OR IT WILL RUST ALL METAL WHICH IS NOT RUST PROOF IN COOLANT PASSAGES. FREEZE PLUGS ETC.

Ah h#*l NO! Coolant has better temperature tolerances and doesn't cause rust in the system like straight water will!! Get coolant put in.

Hmmmm. WATER BOILS at 212 degrees Fahrenheit , your cooling fans don't normally kick on until 215-220.......Be safe and get the right mix in there PRONTO!