Started fishing my local river, (Mississippi, below lock an dam 14) about a month ago. Warm Feb. H20 temp was 36°. Caught a few . Temp went up to 42° started to pick up a few more.
Then cold spell and snow.
Back to 34°.... GOING back down tomorrow to try it.. how do you think that will effect the spawn?
Typically the next 2 wks the fish really move in. And I'm sure that will happen again.
Air temps the next couple wks look for a slow warmth.

H20 temp is a factor (main) but also is length of daylight. From Sam Anderson-- "While this last item (length of daylight) is an arguable point, I know for a fact that fall feeding patterns are trigged by the day light hours, an item for a future article. The reason I believe this is a factor is the fact that on late ice-out years, the walleyes will spawn under the ice.-- To provide ideal spawning conditions the water temperature should warm slowly and constantly with no severe temperature swings or wave action during the gestation and hatching period. The north and east shorelines are usually the areas where the majority of the walleyes spawn. While the fish do not know east from west or north from south, what makes these shore lines most desirable is the fact that the sun penetrates the north and east shore lines with the hottest sun of the day. Therefore, the water is the warmest close to shore and in some cases, the ice can be ten feet from shore with the lake covered with ice, yet the walleyes will spawn.--When the spawning ritual is complete, these battered and exhausted fish move to the deepest structure of the lake to rest for four to ten days. After the rest period, the walleyes are eminently hungry and that's when they move back to their spawning areas and the early spring action is at its best. "

So I would think an ideal year would be right when perfect water temps (mid 40's) coincide with perfect length of day. This is probably a normal ice out situation IMO-- or within a week or so of it, give or take significant weather changes.

If 42 is all it got, I don't think it fully happened yet. 44-46F is what I have heard for full out spawn for N Lakes,, warmer in the S. A warmup then another significant cold spell I think would mess with them to degree that it may screw them up even more,, but right now I think your OK.
The walleye spawn fascinates myself. Since 1999 I have tripped in May on and around the opener 16 times. I think? I have learned a great deal about the walleye spawn in those years. In 2013 (record late ice out for many lakes) we actually switched from Kawishiwi Lake entry (Malberg) to the Little Gabbro (River) entry due to ice still on KAWISH. Water temp on SAT of opener on the river was 38F-- Sunday was about the same,, maybe 39 from my memory with Monday being 39-40 on avg. We fished hard and everywhere without a single walleye ( a few pike). Then Tuesday it got VERY WARM with Ely seeing 79F and the water warming to 42F. We were staying at the Hilton Site on the Kawish any my buddy and I were fishing the S side,, while other buddies were fishing the N side. Flowage on both sides right next to the rapids. Buddy and I both had slip bobbers out and were literally calling it and saying lets see what the boys are doing on the others side as we had a pull of Schnapps --- we turned around to reel in and both bobbers were gone and we reeled in two 15"ers. Casted back out and nothing and then it got too dark. Water temp 42F. The next day was take out day. I wish we could have stayed another couple of days and dial it in.

Awesome post WhiteWolf.

Yogi they haven't gone anywhere......they are there but maybe a bit lethargic......... now you just have to get them to chew. I would be interested in vertical jigging with a few pieces of shiner minnow on a jigging rap. Try and aggravate them and get a reaction bite.

Heres another thought........how much current is there? On the St Clair river we would anchor up and fish pencil plugs. They float but you put them on a 3 way set up with a heavy weight. Then you lift and drop, lift and drop fishing them mostly in the same place. Very effective even in cold water (we went at night in the cold water of the St Clair river).

Pencil plug fishing set up

pencil plug

You start to get some walleye to spawn in the low 40's but 46 degrees gets them going. Your going to need more than one day. Yes daylight also matters and on average around April 20th is a good peak date for walleyes spawning in the Mille lacs area.
They say a late spring usually has a better chance for a excellent walleye hatch. Reason is once the eggs are laid if the water cools down or stays cold the walleye eggs will sit there and more apt to suffer some natural event causing a poor hatch. A steady gradual warmup is best.