Familiarity with seasonal correlations between weather and hatches is important, but variations in daily weather patterns are likely to have a more profound influence on angling tactics.

Sunshine vs. Overcast

As a fly shop employee I was always amused by the effect of weather on guides and clients when they met at the shop prior to a trip. On a glorious sunny morning — whether April or June or September — inexperienced clients would be cheerful and talkative as a Montana meadowlark on a prairie fencepost, while their guide would be scowling and muttering to himself as he picked out flies for the day. However, given a morning of heavy overcast and a little drizzle, the clients would ask lots of nervous questions about cancellation fees and raingear, and the guide would be happy as a clam.

This behavior reflects one of the most basic generalizations about weather and spring creek fishing: clouds are an angler's best friend. Both trout and aquatic insects tend to be more active in low light, and cloudy conditions spread these light conditions over a longer part of the day. The fish are afforded better protection from aerial predators in low light, making them feed more confidently in the clear waters of a spring creek or tailwater. In addition, the eyes of trout are capable of relatively rapid adjustment to changes in light intensity, so they have an advantage over their prey in low light. (For a very informative account of the senses of gamefish, see Through the Fish's Eye by Mark Sosin & John Clark.)

The timing and density of hatches also favors the angler on overcast days. On warm, bright days, hatch activity usually starts earlier in the day but will be shorter in duration, often producing brief but very intense activity. Conversely, on cloudy days, hatches show a later onset, but will produce steady numbers of bugs for a longer period of time. This information is key for an angler planning the day's tactics based on weather conditions. On a practical level, longer hatches give the angler a better opportunity to make some mistakes and still have a chance to catch a good number of fish. During very intense hatches, the angler sometimes struggles to get his fly noticed among a raft of naturals. The time taken to change flies or untangle a leader may also burn up a large portion of the trout's feeding activity. The wings of mayfly duns dry more slowly in the cooler air temperatures and higher humidity of an overcast day. The result is an emerging insect that stays on the water longer, making them more vulnerable to the fish — this often allows the angler to switch to more visible dun patterns, rather than relying on emergers through most of the hatch.

The one advantage to bright conditions is that it makes spotting fish below the surface much easier. Of course, in many cases, hatches will be heavy enough on cloudy days that spotting fish will be no more difficult than looking for rise forms.

As an angler or guide, bright morning sun on a spring creek doesn't scare me. I make use of the good high-angled spotting light on these days to look for nice fish suspended over submerged weed beds. Sight fishing with a midge larva or small mayfly nymph can be deadly in these conditions.

Although fully mature aquatic insects are capable of delaying their emergence for optimal hatch conditions (see Fred Arbona's The Mayflies, the Angler, and the Trout), anglers should recognize that mid-summer insects are adapted somewhat to hatching in sunlight, so you are likely to see hatches and feeding fish, even on bright days. If you fish a western spring creek in early July, you will see some Pale Morning Dun mayflies in almost any weather, but the hatch (and fishing) are likely to be even better if you luck into a cloudy day.

Rain and Snow

Most experienced anglers can think back on the best fishing days in memory and find that a good number of them came on days when it was raining or snowing. Precipitation can have a positive effect both on hatch activity and the fish's willingness to feed. A number of reasons can be given for this. One obvious (but often ignored) reason is that rain or snow comes on days with overcast skies. The mixing action of rain hitting the water's surface also oxygenates the water, which may raise the activity level of the fish. Rain can also moderate extreme water temperatures, warming cold flows early and late in the season, while an afternoon thundershower can cool warm flows in mid-summer.

My experience is that the best hatch activity and fishing is often not during the precipitation itself, but immediately after it (or in between showers or snow flurries). The high humidity associated with precipitation is also conducive to hatch activity and fishing success for the reasons noted above.

Barometer

Like most anglers, I am convinced that barometric pressure affects fishing, but I don't think any angler can profess to explain all of its effects. One reason for this is that barometric pressure has a complicated interrelationship with other weather factors we have discussed so far: air temperatures, water temperatures, light intensity, etc. I would agree, for the most part, with Gary Borger's characterization in Presentation, that a rapidly changing barometer is usually a problem, and a steady or slow change in barometric pressure will allow for good fishing. (See also the "Sunshine and Shadow" chapter of Trout.)

The weather conditions I dread — as a spring creek angler or guide — are days of unsettled, "squirrelly" weather. On days when small fronts are zipping all over the weather map, most guides would prefer to stay home and hide under the covers. On these days, gusty winds change direction constantly, scudding clouds preclude either good spotting light or steady overcast, and a changing barometer seems to keep both bugs and fish at minimal levels of activity.

Gearing Up for Weather

Being able to make some basic predictions about hatches and fish activity because of weather conditions can be a key part of planning one's tactics for the day. It is equally important to be prepared to fish (comfortably) in any possible weather conditions. Here are a few suggestions on necessary gear for a day on a spring creek or tailwater.

Polarized sunglasses are an absolute must for any fishing, but they are especially critical for the spotting required on spring creeks and tailwaters. Stash a spare pair in your vest or fishing bag (even if they are inexpensive backups) in case you lose or break a pair. For sun protection, be sure to use waterproof sunblock (don't get so excited to start fishing that you don't take time to put it on until you are burned) and wear a brimmed hat. Nothing can ruin a fishing vacation faster than a bad sunburn on the first day of the trip.

If you fish in higher altitude locations, you know that rapid temperature changes are a common occurrence, so even in the warmest part of the summer carry a fleece jacket or pullover for insulation if the weather cools off. Fishing in the spring and fall calls for a warm hat (that covers the ears) and warm gloves. Fingerless gloves are very popular, but I have always found them a sure way to get the tips of one's fingers cold. I prefer to wear a full fingered glove that gives me enough dexterity to handle line. When I need to tie a knot or unhook a fish, I take the gloves off and stuff them in tops of my waders or in an inside pocket. I also carry a small towel, so that if my hands get wet, I can dry them completely before donning the gloves again.

You should carry the best quality raingear that you can afford. A breathable rain jacket also doubles as a windbreaker on blustery days. Raingear in the trunk of the car (or worse, back in the motel room) offers little protection, so choose a jacket that you are willing to pack along.

Packing the right clothes and gear allows the angler to concentrate on the fishing situation, rather than frozen fingers or the stream of cold rain dripping into one's collar. Packing and dressing intelligently for a variety of weather conditions is an important part of fishing tactics. In next part, we discuss how to deal with a special weather condition: wind.

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