Another cold week with rain and snow has sped up the cooling process on the lakes and has many of the deep lakes beginning to turn over. Anglers can see the dead algae floating on the surface of the lakes in the mornings, before the wind has a chance to mix the algae back into the water. Algae dies quickly when the water temperatures drop and will remain at low levels during the winter. Algae will spike again in the spring after ice-out when water temperatures begin to rise.
Cold and wet would accurately describe this past week in the Bemidji area. The fall colors are near their peak, with the leaves getting blown and rained off trees at a fast rate. After a warm first three weeks in September, the temperatures ironically dropped dramatically once fall officially arrived on the calendar. The fish had been staging to make their move into deeper water as soon as the thermocline disappears in the lakes. Many lakes still had a visible thermocline early in the week, but by the end of the week, the thermocline was gone from most lakes.
October is on the doorstep as another month has nearly gone by. The first frost of the season was this week, so those troubled by allergies should be getting a little relief soon. The leaves have started to change color, with this week and next weekend close to the peak viewing in most of Northern Minnesota. The wind and the rain will knock the leaves off the trees fast, so sooner is better for those who want to see the fall colors near their peak.
The fall cool down resumed in earnest this past week, after what was probably one last fling with the upper 70s through last weekend. Surface water temperatures in many lakes rose back to around 68 degrees after a string of unseasonably warm days last week. Surface water temperatures have been dropping almost one degree per day when the temperatures stay in the 50s for the highs and 40s for the lows. The slowly declining temperatures may be here to stay this time, with the first frost of the fall likely to happen soon.
The warm fall weather continued this past week, with surface water temperatures holding in the mid-60s, with some lakes warming slightly back into the upper 60s. A slow but steady cool down prolongs the best fishing in the fall, with the best fishing still ahead of us in the Bemidji area. A sudden cold snap would quicken the process of cooling down the lakes, but the fish don't like anything to change too fast, or they usually respond negatively for a period of time until the conditions stabilize.
The fall cool down continues as surface water temperatures in the lakes drop to the mid-60s. Fall fishing patterns can be slow to develop after a long hot summer, but by the time surface temperatures cool down to about 65 degrees, the fish have already started to move and get more active. It is the same thing when fish get more active in the spring as the water warms as it is in the fall when fish get more active as temperatures cool in the fall going through the same temperature range.
The dry weather pattern in the Bemidji area finally broke this past week, with several days with measurable rain. People's lawns were brown and dry if they were not being watered, but everything responded quickly to the much needed moisture, which should lower the fire danger in the area. Rain is usually part of the fall cool down in the lakes, with the September rains usually coming down at a cooler temperature than the water in the lakes.
The second peak of the summer for water temperatures likely occurred earlier this past week, with most lakes reaching the mid- to upper 70s for the second time this summer. The extended forecast for the Bemidji area is predicting highs in 70s and lows in the 50s most days in the near future, which would slowly begin to cool down the water in the lakes. The fall cooldown is seldom a straight line, with ups and downs along the way. It is usually a gradual trend that works in reverse of the spring, only with the lakes cooling off instead of warming up.
This past week may have been the last string of days with temperatures in the 80s for this summer. Then again, maybe not. There isn't a distinct cool down in the extended forecast yet, but temperatures are expected to moderate slightly next week with highs in the 70s, which is nearly perfect weather for most outdoor activities. The smoke in the air has been more noticeable on days with winds from a westerly direction, from fires all up and down the West Coast and Canada.
Water temperatures in the Bemidji area lakes are going up again after a week with highs in the low 80s. Most lakes now have surface temperatures in the mid-70s in the mornings, before the sun has had a chance to warm the water. The water temperatures are not high enough to cause most fish problems, but they are high enough to keep metabolism levels elevated for the fish. Everything has to eat more to keep up with the calories they are burning.