I can reliably get my wort down to around 50° F in any weather. Of course, I only go that far for lagers. For ales, I stop once I hit 65° F.
I use a plate chiller, a camping cooler full of ice water, and 2 pumps. One pump circulates wort through the plate chiller and back into the kettle (NOT into the fermenter). The other pump circulates the ice water through the plate chiller in the other direction. I just use plain tap water from the hose until the wort reaches 100° F, then I switch over to the pump/ice water (no sense wasting perfectly good ice). My ice bath consists of a camping cooler with 7-8 frozen juice bottles, a bag or two of ice from the grocery store, and half-filled with water. If I've been planning ahead, I'll actually take a bucket of tap water a few days ahead of time and stick it in my beer fridge to get it as cold as possible before brewing.
Once the wort has cooled to the desired temperature (according to the thermometer mounted on my kettle), I cease chilling and rack the wort to a fermenter with a plain old autosiphon (alleviating any issues with the dip tube losing siphon and ensuring I can get every drop of good wort from the kettle).
I get from boiling to 100° F in about 3 minutes. Getting down to 65° from there takes another 5-10 minutes.