B737 Captain reported a cockpit window failure while in climb to cruise altitude. The Captain diverted to a nearby airport and landed safely.

Narrative

I was the Pilot Flying in the left seat on Flight XXX; ZZZ-ZZZ1. As we were climbing out of FL230; I noticed arcing in the heating element of the left side; forward windshield (L1). I called for the Arcing Windshield QRH; which the First Officer found under the Window Damage - Forward section. The QRH called for the window heat switch of the affected window to be turned OFF; which we did. We completed the QRH for an arcing window and less than a minute later; the L1 Window cracked; with a loud snapping sound. Within another 30 seconds we heard and saw another crack streak across the same window. By now we had reached FL250; and we asked ATC for an immediate descent to 10;000 ft. because I was concerned about more extensive damage to the window. I called for the First Officer (FO) to continue the Window Damage QRH - Cracked or Shattered part of the same section. We continued descending and finished the QRH. We determined that the cracking was on the outer pane of the L1 window. Even though the QRH directs continued normal operations for outer pane cracking; I used my Captain's emergency authority to determine that the safest course of action was to divert to ZZZ2. We informed ATC of our intentions and they asked for the number of souls on board and amount of fuel in time. An [priority was requested]; and emergency equipment was standing by in ZZZ2. I called the Flight Attendants with X chimes and told the A Flight Attendant (F/A) that we had experienced a cracked window and were descending to divert; that we would be landing in 12 minutes and to secure the cabin for arrival. I also told him to expect a normal landing and taxi to the gate. Then I made a PA to the Passengers informing them that; out of an abundance of caution; we were diverting to ZZZ2 due to a Maintenance issue. ATC had informed Dispatch of our intentions; and we received an amended release over ACARS for our diversion to ZZZ2. I reprogrammed the FMC for our arrival to ZZZ2 while the FO obtained the ATIS and ran the numbers for landing. I asked for the Diversion Plan on the checklist; and we reset the pressurization for ZZZ2 field elevation; as well as making sure all the other items on the Diversion Plan had been addressed; which they were. By now we were nearing the airport and getting vectors from ZZZ2 approach for Runway XXL. The weather was > 10 miles visibility and clear skies. We discussed the overweight landing and agreed to run the brake cooling numbers after we landed. We made a normal landing and exited Runway XXL using minimal wheel braking (initiated less than 80 knots). I stopped the aircraft on Taxiway 1 and held the brakes with the foot pedals while I spoke with the Fire Chief on a discreet frequency. I asked him to inspect the main gear for any sign of damage. He used a heat gun and said temperatures were normal. Meanwhile; the FO ran the numbers for brake cooling; and we received the message that limits had not been exceeded; meaning we could continue to the gate. The fire trucks followed us to the gate. We parked; shutdown and the Passengers deplaned normally through the forward entry door. I filled out the aircraft logbook for the arcing/cracking windshield and the overweight landing (separately). I called Dispatch and spoke with the manager of Dispatch about the flight. I also spoke with Maintenance Control about the write ups in the logbook. We left the aircraft with ZZZ2 local Maintenance. I debriefed the F/A's and the FO; and we all found ourselves in adequate condition to continue to ZZZ1 (on a different aircraft); which we did with all but 2 Passengers who deplaned in ZZZ2. That flight was operated without incident to ZZZ1.I do not feel anything could have prevented the malfunction. With one small crack in the outer pane I would have felt more confident continuing the flight to ZZZ1 as the QRH allowed. But with two large; deep crack across the L1 window; I was concerned that more cracks could develop and compromise the integrity of the window. I felt the safest course of action was to divert; especially since we were close to ZZZ2 at the time of the malfunction.