B777 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 10993; Flight Crew Type 3336
Situational Awareness
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Inflight Event / Encounter Weather / Turbulence; Inflight Event / Encounter Loss Of Aircraft Control
Air Traffic Control Issued New Clearance; Flight Crew Diverted; Flight Crew Regained Aircraft Control
Weather
We talked to dispatch prior to departing regarding forecast for thunderstorms in ORD with the best alternate being MSP. When approaching the MSP area we talked to dispatch again and told him we would hold over MSP until the thunderstorms passed over ORD. He responded that they were changing the arrival around the thunderstorms and that the weather was dissipating. We also pulled up ZZZ weather and it had improved to VFR. We told dispatch we would continue on the approach and if we encountered any problems we would go to ZZZ. As we continued ATC changed the arrival again; from North arrival to East arrival over the lake. As we were being vectored for the localizer the radar return for the area was solid yellow with areas of small speckled red. We experienced moderate turbulence during the descent in IMC conditions. About 15 miles from SEIKA we had to deviate South to avoid some red speckled areas. We were heading approximately 310 to intercept localizer just outside SEIKA. Descending from 4;000 to 3;000 about 6 miles Southeast of SEIKA at flaps 1 and speed 210. At about 3300 ft; approximately 6 miles out from SEIKA we experienced severe windshear. The airspeed went from 210 to 180 for approximately 3 to 4 seconds which caused the airplane to descend.  I increased powered to approximately max continuous. This was immediately followed by a sudden windshear induced airspeed increase to approximately 230 knots. I responded by pulling the throttles to idle. Before I could get the throttles to idle; the airspeed again suddenly dropped to 190 knots and we experience a lightning strike. The co-pilot had been calling out the airspeed changes. At this point the co-pilot vehemently expressed that he was really uncomfortable with this situation and he thought we should go to ZZZ. I agreed and he told approach control we needed to climb to 10;000 feet and needed deviation around weather to go to ZZZ. I pushed the go around paddle to immediately escape the windshear (when I did that I accidentally turned off the auto throttle with my thumb and asked my co-pilot to restore the auto throttle). We climbed to 10;000 feet; picking our way through the weather and proceeded uneventfully to ZZZ. Being task saturated; I did not declare an emergency since ATC gave us the clearance we needed to avoid any further problems. In retrospect I probably should have declared an emergency.
B777 Captain reported encountering severe turbulence; windshear; and lightning during approach to ORD and diverted.