EMB ERJ 170/175 ER/LR
Flight Crew Air Transport Pilot (ATP)
Workload
Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach; Inflight Event / Encounter Weather / Turbulence
Flight Crew Became Reoriented; Flight Crew Took Evasive Action; General Maintenance Action
Procedure; Weather
Over the 10 DME fix on the ILS; we had a strong rain shaft at an 8 DME from the runway that we had to fly through which looked like it was stable but had very strong 20Kts+ windshear gain. Before we  entered the PF (Pilot Flying) determined to try to get configured partially for the approach which is also SOP and I had no  objections we selected Flaps 1 at 210kts and after they were set we entered the rain. As we descended I called out rising airspeed; at that time the PF already had Spoilers deployed and thrust levers at IDLE; he called for the gear after we couldn't stabilize the airspeed and reached around 237 kts before the gear was able to assist in slowing the aircraft. The flaps continued to work for the rest of the approach and had no issues getting on the ground. The weather was due to the developing Nor-Easter in the area and we were the first aircraft to report the 20kt+ gain on final.We could've called for the gear sooner when I noticed the speed increase but not sure if that would have even stopped the gain it jumped quickly and suddenly from 210 to 228 to 238.
An ERJ-175 pilot reported windshear on final which resulted in a 20 kt increase. Speed brakes and landing gear were extended to regain a stable profile for landing.