Bad Sun Angle.
With early morning or evening matches the sun can present an extreme problem at one end of the field.
Decide which end of the field will be impacted.
Decide if the impact will be worse during the first half or the second half of the match.
Take into consideration weather conditions - are clouds on the horizon and will they arrive by the second half?
You should also consider the competitive balance between your team and the opponent.
In general I will take the end of the field that provides my team with an advantage in the first half. This is especially true if a rising sun, a setting sun or clouds on the horizon might diminish the hazard by the time the second half arrives. If in doubt, ask your Goalkeeper which half (s)he prefers to take first.
Of course, it might be the opponents win the coin flip and have the choice of which half they wish to take first. If this is the case tactical adjustments might be necessary. Employing a high line of confrontation in an attempt to play most of the half on the opponents end might be a consideration. Deciding to "force' the ball to a certain side of the field as a means to reduce shots originating directly from the angle of the sun might be considered. Having the GKer wear sun glare strips is an option to consider.
Rain presents two basic issues that must be dealt with.
1) A wet and slippery ball can skip causing misplays. This can be bad for field players and disasterous for goalkeepers.
2) A wet surface can cause players to slip, slide or fall resulting in missed plays and misplays.
A key consideration for playing on a slippery surface is to keep one's weight over their feet. Players will slip or their feet slide out from under them when their feet are positioned wider than their hips. This can necessitate players changing normal pursuit angles so they find themselves at a point where the ball will be instead of going directly to the ealiest point to intercept the ball. Getting in front of the ball takes on added importance.
It can also necessitate players shortening their strides as the point for making a play approaches. This is especially true if a change of direction is necessary. It is the planting of one's foot outside of the hips or out from under the body's weight that causes slips, slides and falls on a wet surface.
Preparing to play the ball by positioning yourself directly in its path whenever possible combined with movement directly to and in-line with the path of the ball is the best prevention for playing a ball that skips. The spin of the ball may alter its course slightly when it skips. The remedy here is to not allow the ball to hit the ground or play it on the short skip before it has a chance to more drastically alter course.
For goalkeepers in particular it is important to attack the ball on a wet. slippery surface. However, the "attack" must be in direct line with the path the ball is traveling. The danger for the goalkeeper is the same as for field players - that his feet will slip from under him when attempting to make a cut or dive to play the ball. Once again, the key is to keep the body's weight over the feet as much as possible.
A third point of emphasis to be considered is communication and resulting organization. The fact is, there will likely be more miscues on a wet, slippery surface be they ball related, player related or both. Effective communication and heightened atention to organization within the concepts of formation and system of play can reduce the number of potential mistakes and minimize the potential damage of mistakes that do occur.
Finally, many of the cleats manufactured today are for a specific ground type. There are hard ground cleats, firm ground cleats and soft ground cleats to mention a few. Expensive boots will have studs that can be shortened or lengthened to play in whatever weather conditions are encountered. Coaches need to remind players that if they have footwear designed for wet conditions that they need to wear these in rainy conditions.
Strong winds can present very real tactical difficulties to consider. If given the choice, take the wind in the first half of the match. There exists the chance the wind could die down for the second half. This can be especially true for twilight games. However, it's always good to check hour to hour weather forecast on a smart phone during pregame. Take every advantage you can, even technological ones brought to you by smart phones.
The general rule of thumb for my teams is to keep as many people behind the ball as possible. With the wind at their backs opponents will try to push up and keep the ball in your defending third. Invite them in to be countered upon. CAUTION: kick and run counter is not likely to work when playing into the wind, but quick passing possession with ground or low driven balls can be extremely effective.
So, when playing into the wind I remind my teams to keep the ball on the ground. Clearances should always be wide and low driven balls, even if they go out of bounds. Playing the ball out of bounds when playing into the wind can accomplish a few different things for your team.
1) Allows time for a team under pressure to organize.
2) It can be a means of trading possession for yardage. If your team is struggling to clear the ball through possession, keep the ball wide and kick it out of bounds up the field. Trading possession for yardage can be a useful tactic. Consider clearing consecutive throw-ins 10 yards up the field. Suddenly you have bought yourself 20 yards of territory and can now attempt to possess without the pressure of being packed back into your defending 3rd.
3) Purposely causing restarts can shorten the time you must play into the wind. Playing the ball out of bounds prompts a throw-in AND provides an opportunity for substitutions. I take full advantage of stoppages in play to substitute players under the unlimited substitution rules here in the US. This takes time off the clock.
I also instruct my GK to take the full 6 seconds he is allowed on clearances before driving the ball low out of bounds as far up the field as possible. When opponents play the ball out of bounds, goalkicks and throw-ins should be taken at a leisurely pace unless a clear tactical advantage can be gained by going quickly.
I instruct my teams to approach free kicks in the same manner. No sense to go quickly unless there is a clear advantage / goal scoring opportunity to be had. Take your time. Set the ball. Ask for your 10 yards. Talk it over with a teammate or two before taking the kick, BUT listen to the referee as well. If he warns you about delaying the game you may have to speed up play a bit.
Taking time off the clock via legal means is a tactical consideration. It can also provide a pyschological advantage as teams playing with the wind often have a sense of urgency knowing they have a waning advantage they need to capitalize on.
Playing with the wind at your back should be addressed with your team as well. Young or inexperienced teams will often attempt to play fast and very direct with the wind at their backs. This can result in a lot of long flighted balls being played "over" the opponents defense that result in little more than keeping the opponents goalkeeper busy collecting them. Don't allow playing with the wind to become a disadvantage to your team. Your team should play its normal game and take advantage of the wind in certain specific situations.
1) Goalkeeper clearances can go quite a bit farther with a stiff wind. Do not try this every time, but set your opponents up to be beaten by a long clearance with it.
2) There is no offside on goalkicks so if an opportunity to execute a goalkick with the wind arises, think of going long.
3) A long free kick can become a shot. In fact, longer shots in general might be possible, but keep them within the frame work of your teams system of play. That is, they should not become your teams system of play. If the opportunity exists, take it, but do not try to manufacture a specific opportunity to take a long shot.
4) Be very mindful that the opponents will likely want to keep the ball outside along the flanks when they are playing into the wind. So it becomes logical to play in the middle of the field when going with the wind. However, the purpose for playing in the middle of the field should not necessarily be to play directly to goal. Remember, long flighted balls with the wind usually serve no purpose but to keep the opposing GKer busy collecting them. Play with purpose in the middle of the field. That purpose being to create space on the flanks to utilize when it is to your advantage to do so.
5) Use the wind to help keep the ball in your opponents half of the field. That is perhaps the best advantage the wind can provide. Don't make it out to be any more of an advantage than it actually is. Doing so might cause your players to let up a bit thinking they have "an extra player" in the wind and that is most certainly not the case. Your team should continue playing their normal game when playing with the wind using the wind to their advantage but not becoming reliant upon the wind to an extent where they sacrifice their normal game for it.
Lastly but perhaps of most importance are commnication and organization. I have been in windy conditions that made communication nearly impossible at more than 15 to 20 yards. This is when it is necessary for everyone to constantly communicate instead of relying on one or two players to do most of the talking. Communication is the key to organization. Staying organized on both sides of the ball is the key to playing in windy conditions.